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STUDIES ON TRANSITION METAL NITROSYL CHEMISTRY by JOHN T. MALITO B.Sc. (Hons.) U n i v e r s i t y of B r i t i s h Columbia, 1972. A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in the Department of Chemistry We accept t h i s t h e s i s as conforming to required standard THE UNIVERSITY OF BRITISH COLUMBIA August, 1976 (3 John T. M a l i t o , 1976 the In presenting this an a d v a n c e d d e g r e e the I Library further for agree in p a r t i a l fulfilment of at University of Columbia, the make it freely that permission for this representatives. thesis for It financial gain of The U n i v e r s i t y of British 2075 Wesbrook Place Vancouver, Canada V6T 1W5 6 for extensive by the Columbia shall not the requirements reference copying of Head o f is understood that written permission. Department British available s c h o l a r l y p u r p o s e s may be g r a n t e d by h i s of shall thesis I agree and be a l l o w e d that study. this thesis my D e p a r t m e n t copying or for or publication without my - ii - ABSTRACT The reactions of . n i t r o s y l c h l o r i d e with a v a r i e t y of anionic and neutral metal carbonyl and n -cyclopentadienylmetal 5 compounds of C r , Mo, W, Mn, Re, Fe and Co are d e s c r i b e d . carbonyl In most cases n i t r o s y l - c o n t a i n i n g complexes are formed in reasonable y i e l d s . The advantages and l i m i t a t i o n s of n i t r o s y l c h l o r i d e as a general s y n t h e t i c reagent f o r the preparation of t r a n s i t i o n metal n i t r o s y l complexes are discussed. The high y i e l d syntheses of CpM(C0) (N0) (M = C r , Mo or W) 2 from NaCCpMCCO)^] and Diazald are d e t a i l e d . Subsequent r e a c t i o n of the d i c a r b o n y l n i t r o s y l species with n i t r o s y l c h l o r i d e affords the corresponding CpM(N0) Cl complexes in e x c e l l e n t y i e l d s . 2 The CpM(N0) R 2 (M = Cr or Mo; R = Me, E t , i-Bu or Ph: M = W; R = Me or-Ph) complexes are obtained in the reactions of CpM(N0) Cl with a l k y l - or arylaluminum 2 reagents. Some f u r t h e r d e r i v a t i v e s of the CpM(N0) Cl complexes and 2 the high y i e l d preparation of [ C p C r ( N 0 ) ] 2 2 are also d e s c r i b e d . Previously unreported compounds are c h a r a c t e r i z e d by i n f r a r e d and nuclear magnetic resonance spectroscopy and by mass spectrometry. ACKNOWLEDGEMENT I wish to thank the technical s t a f f and f a c u l t y of t h i s department f o r t h e i r assistance and support. In p a r t i c u l a r , I am indebted to Dr. B.R. James, Dr. R. Stewart and Dr. A. Storr who read t h i s t h e s i s and made suggestions f o r improvement. A l s o , the aid and thoughtful d i s c u s s i o n offered by Dr. A . E . Crease and Mr. B.W.S. Kolthammer are g r e a t l y appreciated. I also thank Miss L. Hon who typed t h i s t h e s i s . I extend my gratitude to Dr. P. Legzdins, whose unshakable optimism, s p i r i t e d humor and companionship provided both encouragement and guidance. - iv - TABLE OF CONTENTS Page ABSTRACT i i ACKNOWLEDGEMENTS iii TABLE OF CONTENTS iv LIST OF TABLES vi i i LIST OF FIGURES ix ABBREVIATIONS AND COMMON NAMES x CHAPTER I, 1 CHAPTER I I , GENERAL INTRODUCTION THE REACTION OF NITROSYL CHLORIDE WITH SOME TRANSITION METAL CARBONYL ANIONS 4 2.1 INTRODUCTION 4 2.2 EXPERIMENTAL 5 2.2a Preparation of n i t r o s y l c h l o r i d e 6 2.2b Preparation of bis(triphenylphosphine)iminium c h l o r i d e , bromide and i o d i d e , (PPh ) NX (X = C l , Br or I) Preparation of bis(triphenylphosphine)iminium pentacarbonylhalotungstates, (PPh-) NW(CO)r-X (X = C l , Br or I) f.t 11 Reactions of n i t r o s y l c h l o r i d e with some anionic and neutral complexex of manganese, rhenium and iron 13 Reactions of n i t r o s y l c h l o r i d e with t r i c a r b o n y l (n -cyclopentadienyl) anions of chromium, molybdenum and tungsten, [CpM(C0)o]~ (M = C r , Mo or W) 15 Reaction of sodium n i t r i t e and a c e t i c a c i d with sodium t r i c a r b o n y l ( n - c y c l o p e n t a d i e n y l ) t u n g s t a t e , Na[CpW(C0) ] 15 3 2.2c 2 9 2.2d 2.2e 8 5 2.2f 5 3 - v Page 2.2g Reactions of n i t r o s y l c h l o r i d e with b i s ( t r i p h e n y l phosphine)iminium pentacarbonylhalotungstates, (PPh3) NW(C0) X (X = C l , Br or I ) , and with t e t r a ethylammonium pentacarbonylchloro(or methyl) tungstate, Et NW(C0) X (X = Cl or Me) 2 5 4 2.2h Reactions of 5 16 tetracarbonylhalonitrosyltungstens, W(C0) (N0)X (X = Cl or B r ) , w i t h tetrahydrofuran 4 ... 16 2.3 RESULTS AND DISCUSSION 18 2.3a Bis(triphenylphosphine)iminium c h l o r i d e , bromide or i o d i d e , (PPh ) NX (X = C l , Br or I) Bis(triphenylphosphine)irninium pentacarbonylhalotungstates, (PPh ) NW(C0) X (X = C l , Br or I) 18 20 2.3c Reactions of n i t r o s y l c h l o r i d e with metal carbonyl anions 22 2.3d Reactions of t e t r a c a r b o n y l h a l o n i t r o s y l t u n g s t e n s , W(C0) (N0)X (X = Cl or B r ) , with t e t r a h y d r o f u r a n . . 30 3 2.3b 2 3 2 5 4 CHAPTER I I I , REACTIONS OF NITROSYL CHLORIDE WITH NEUTRAL METAL CARBONYL COMPLEXES - 32 3.1 INTRODUCTION 32 3.2 EXPERIMENTAL 35 Reactions of n i t r o s y l c h l o r i d e with neutral complexes of iron and cobalt 35 3.3 RESULTS AND DISCUSSION 37 3.3a Reactions of n i t r o s y l c h l o r i d e with pentacarbonyli r o n , Fe(C0) Reaction of n i t r o s y l c h l o r i d e with b i s [ d i c a r b o n y l (n -cyclopentadienyl)iron], [CpFe(C0) ] Reactions of n i t r o s y l c h l o r i d e with t r i c a r b o n y l n i t r o s y l c o b a l t , Co(C0)3(N0), and d i c a r b o n y l ( n c y c l o p e n t a d i e n y l ) c o b a l t , CpCo(C0) 3.3b 5 5 3.3c 2 2 37 39. 5 9 40 - vi - Page CHAPTER IV, CYCLOPENTADIENYLNITROSYL COMPLEXES OF CHROMIUM, MOLYBDENUM AND TUNGSTEN 42 4.1 INTRODUCTION 42 4.2 4.2a EXPERIMENTAL Preparation of d i c a r b o n y l ( n - c y c l o p e n t a d i e n y l ) n i t r o s y l complexes of chromium, molybdenum and tungsten, CpM(CO) (NO) (M.= C r , Mo or W) 46 Preparation of c h l o r o ( n - c y c l o p e n t a d i e n y l ) d i n i t r o s y l complexes of chromium, molybdenum and tungsten, CpM(N0) Cl (M = C r , Mo or w) 48 Preparation of ( n - c y c l o p e n t a d i e n y l ) i o d o d i n i t r o s y l complexes of chromium, molybdenum and tungsten, CpM(N0) I (M = C r , Mo or W) 50 Preparation of b i s [ ( n - c y c l o p e n t a d i e n y l ) e t h o x o nitrosylchromium], [CpCr(NO)(0Et)] 50 Preparation of b i s [ c h l o r o ( n - c y c l o p e n t a d i e n y l ) nitrosylchromium], [CpCr(N0)Cl] 51 Preparation of a l k y l - and a r y l - ( n - c y c l o p e n t a d i e n y l ) d i n i t r o s y l complexes of chromium, molybdenum and tungsten, CpM(N0) R (M = C r , Mo or W; R = a l k y l or aryl) 52 Preparation of b i s [ ( n - c y c l o p e n t a d i e n y l ) d i n i t r o s y l chromium], [ C p C r ( N 0 ) ] 55 4.3 RESULTS AND DISCUSSION 58 4.3a The d i c a r b o n y l ( n - c y c l o p e n t a d i e n y l ) n i t r o s y l complexes of chromium, molybdenum and tungsten, CpM(C0)~(N0) (M = C r , Mo and W) 7 58 The c h l o r o ( n - c y c l o p e n t a d i e n y l ) d i n i t r o s y l complexes of chromium, molybdenum and tunqsten, CpM(N0) Cl (M = C r , Mo or W) 7 59 Bis[(n -cyclopentadienyl )ethoxonitrosylchromium, [CpCr(NO)(0Et)]2, and b i s [ c h l o r o ( n - c y c l o p e n t a d i e n y l ) nitrosylchromium, [CpCr(N0)Cl] 66 2 4.2b 5 2 4.2c 5 2 4.2d 5 2 4.2e 5 2 4.2f 5 9 4.2g 5 2 4.3b 2 5 5 9 4.3c 46 5 5 5 9 - vii - Page 4.3d The a l k y l - and a r y l - ( n - c y c l o p e n t a d i e n y l ) d i n i t r o s y l complexes of chromium, molybdenum and tungsten, CpM(N0) R (M = C r , Mo or W; R = a l k y l or a r y l ) 70 Bis[(n -cyclopentadienyl)dinitrosylchromium, [CpCr(N0) ] 78 CONCLUSION 83 5 2 4.3e 5 2 CHAPTER V, 2 - vi i i - LIST OF TABLES Table I Page Elemental Analyses and Physical Properties of (PPh ) NW(C0) X (X = C l , Br or I) 12 Reactions of N i t r o s y l Chloride with some Complexes of Rhenium and Iron 14 3 II III 2 5 Reactions of N i t r o s y l Chloride with (PPh ) NW(C0)rX 3 2 (X = C l , Br or I) and Et NW(C0) X (X = Cl or 4 IV V 5 CH r... 3 Reactions of N i t r o s y l Chloride with some Neutral Complexes of Iron and Cobalt 36 Elemental Analyses and Physical Properties of CpM(N0) X (M = C r , Mo or W; X = Cl or I) 49 Reaction Conditions and P u r i f i c a t i o n Methods f o r CpM(N0) R 53 2 VI 2 VII Elemental Analyses and Physical Properties of CpM(N0) R 56 2 VIII IX X IR and H NMR Data f o r CpM(N0) R Complexes 57 ] 2 High Resolution Mass Spectral Data f o r CpCr(N0) Cl XII XIII 63 2 Low Resolution Mass Soectral Data f o r CpM(N0) Cl 9 (M = Mo or W) XI 17 64 7 Low Resolution Mass Spectral Data f o r [CpCr(N0)X] 2 •• 69 Mass Spectra Fragmentation Data f o r CpM(N0) R 74 Low Resolution Mass Spectral Data f o r [CpCr(NO),], . . 81 2 - ix - LIST OF FIGURES F l >re Page 1. 2. Apparatus f o r P u r i f y i n g N i t r o s y l Chloride ] H NMR of (n -C H )Mo(N0) CH CH 5 5 5 2 2 3 7 72 - X - ABBREVIATIONS AND COMMON NAMES The following abbreviations and common names, some of which are presently used i n the s c i e n t i f i c l i t e r a t u r e , are employed throughout this thesis. o Angstrom A A1R t r i a l k y l ( o r aryl)aluminum 3 amount Amt. butyl Bu n-Bu 0 2 calcd. cm compd. di-n-butyl ether cal culated wave numbers i n r e c i p r o c a l centimeters compound pentahapto-cyclopentadienyl, n -CgHg 5 Cp dec. Diazald diglyme DME Et EtpO EtOAc EtOH h decomposes N-methyl-N-nitroso-p-toluenesulfonami de bis(2-methoxyethyl)ether 1,2-dimethoxyethane ethyl diethyl ether ethyl acetate ethanol hour(s) Hz Herz, cycles per second IR infrared J magnetic resonance coupling constant i n c y c l e s per second 3,4-lutidine 3,4-dimethyl pyridine m medium Me methyl m/e mass to charge r a t i o min. minute(s) mm m i l l i m e t e r s of mercury - xi abbreviations and common names (cont'd) NMR : nuclear magnetic resonance 4-picoline : 4-methylpyridine Ph : phenyl PPh.j : triphenylphosphine : pyrazoyl R : a l k y l or aryl R.p : perfluoroal kyl s : strong Temp. : temperature THF : tetrahydrofuran w : pz - weak n 3 : trihapto- n 5 : pentahapto- v : s t r e t c h i n g frequency T : NMR chemical s h i f t i n parts per m i l l i o n - 1 - CHAPTER I GENERAL INTRODUCTION Numerous t r a n s i t i o n metal n i t r o s y l compounds are known and the development of t h e i r chemistry, which has been the subject of several reviews ( 1 , 2, 3 ) , has c l o s e l y p a r a l l e l e d that of the metal carbonyl complexes. Consequently, i t has been recognized f o r some time that n i t r i c oxide can bond to metals in a manner quite d i f f e r e n t from carbon monoxide. The s t r u c t u r e s o f a number of n i t r o s y l compounds (4) s t r i k i n g l y demonstrate the v a r i a b l e nature of the m e t a l - n i t r o s y l bond, which has a l s o received considerable a t t e n t i o n from a t h e o r e t i c a l of view (5). point In p a r t i c u l a r , two bonding modes have been observed which are best represented by the Lewis structures I and II. Structure I i s characterized by a l i n e a r M-N-0 bond and an M-N bond distance which M=N = 0 i M-_N n strongly suggests the existence of m u l t i p l e bond c h a r a c t e r . In t h i s instance the n i t r i c oxide ligand formally behaves as a t h r e e - e l e c t r o n donor. This type of bonding i s by f a r the most common among the complexes studied to date. In structure II the n i t r o s y l group formally acts as - 2 - a one-electron donor and the M-N-0 bond angle i s 120°. M-N bond i s longer than i n the l i n e a r bonding mode, i t Although the is still somewhat shorter than the expected s i n g l e M-N a-bond d i s t a n c e . While both of these l i m i t i n g structures have been observed, most of the complexes have M-N-0 bond angles which range from 120° to 180°. The use of metal n i t r o s y l complexes as. s p e c i f i c homogeneous c a t a l y s t s has generated much recent i n t e r e s t . For example, F e ( C 0 ) ( N 0 ) 2 2 c a t a l y t i c a l l y dimerizes butadiene to 4 - v i n y l c y c l o h e x - l - e n e , and isoprene to a mixture of 1 , 4 - d i m e t h y l - 4 - v i n y l 1-ene (6). Interestingly, and 1,5-dimethyl-5-vinylcyclohex- both of these dimerizations occur even i n the presence of other o l e f i n s , Lewis a c i d s , or Lewis bases. the Rh(NO)(PPh^)^ complex has been found to c a t a l y t i c a l l y Furthermore, hydrogenate both terminal and c y c l i c o l e f i n s under ambient conditions (7). If this hydrogenation i s performed i n the absence of peroxides or 0 , accompanying 2 o l e f i n isomerization does not occur and the c a t a l y s t may be recovered unchanged. Metal n i t r o s y l complexes f i n d t h e i r greatest a p p l i c a t i o n i n the f i e l d of o l e f i n d i s p r o p o r t i o n a t e the M ( N 0 ) X L 2 2 2 (8). (M = Mo or W; X = C l , Br or I; Most commonly used are L = phosphines, phosphites, arsines and amines) complexes i n conjunction with an organoaluminum c o c a t a l y s t such as M e A l C l 3 2 3 or A l C l . 3 Bearing i n mind the i n t e r e s t i n g bonding, s t r u c t u r a l , catalytic and r e a c t i v i t y properties of metal n i t r o s y l complexes, the development of new s y n t h e t i c routes to these compounds must surely be welcomed. A - 3 - perusal of a review a r t i c l e (9) which deals e x c l u s i v e l y with the preparation of metal n i t r o s y l compounds reveals the obvious lack of a general preparative route. This f a c t i n i t s e l f i s not s u r p r i s i n g since a large v a r i e t y of metals i s encompassed. Unfortunately, many of the e x i s t i n g synthetic routes produce the desired product i n low y i e l d and/or with much expenditure of e f f o r t . The work i n t h i s t h e s i s i s presented i n the s p i r i t of developing new synthetic techniques which, i n a d d i t i o n to y i e l d i n g e x i s t i n g compounds more c o n v e n i e n t l y , may also be applied to the synthesis of new metal n i t r o s y l complexes. studies presented i n Chapter II and III The are exploratory i n nature. For i n s t a n c e , the scope of the reaction of n i t r o s y l c h l o r i d e with a v a r i e t y of anionic and neutral organometal1ic complexes i s o u t l i n e d . Chapter IV describes i n d e t a i l the successful a p p l i c t i o n of t h i s and other s y n t h e t i c methods during the preparation of a v a r i e t y of h a l o - , a l k y l and a r y l - ( n - c y c l o p e n t a d i e n y l ) n i t r o s y l 5 and tungsten. complexes of chromium, molybdenum - 4 - CHAPTER II THE REACTION OF NITROSYL CHLORIDE WITH SOME TRANSITION METAL CARBONYL ANIONS 2.1 Introduction The f i r s t and only reported r e a c t i o n of n i t r o s y l chloride with a t r a n s i t i o n metal carbonyl anion involves the synthesis of (RB(pz) )M(C0) (N0) from [ ( R B ( p z ) ) M ( C 0 ) ] ~ (RB(pz) = 2 3 3 3 borate; R = H or p z ; M = C r , Mo or W) ( 1 0 ) . 3 tris(pyrazoyl)- In s p i t e of the large number of r e a d i l y obtainable metal carbonyl anions ( 1 1 ) , t h i s type of r e a c t i o n has been completely ignored. to which n i t r o s y l A study to determine the extent c h l o r i d e can be employed as a general reagent f o r the synthesis of neutral n i t r o s y l complexes, from the corresponding carbonyl anions, was therefore undertaken. The g e n e r a l i t y of this s y n t h e t i c approach as well as i t s l i m i t a t i o n s , are herein c l e a r l y delineated. nitrosyl In many i n s t a n c e s , t h i s new route affords the desired complexes more conveniently and in higher y i e l d s than was previously p o s s i b l e . Furthermore, the need f o r organometallic anions which are soluble i n non-donor solvents has l e d , during the course of t h i s work, to the e f f i c i e n t (PPh ) NW(C0) X 3 2 5 and high y i e l d synthesis of (PPh ) NX and (X = C l , Br or 3 I). 2 - 5 - S p e c i f i c a l l y , t h i s chapter describes the reactions of n i t r o s y l c h l o r i d e with the f o l l o w i n g s p e c i e s : (PPh ) NMn(C0) , 3 2 5 Na[Re(C0) ], Ph SnRe(C0) , N a [ F e ( C 0 ) ] , Na[CpFe(C0) ], CpFe(CO) SnPh , 5 3 5 2 4 2 2 3 Na[CpM(C0) ] (M = C r , Mo or W) and A[W(C0) X] (A = ( P P h ) N ; X = C l , Br or 3 A = E t ^ N ; X = Cl or Me). 5 3 2 The chemical and physical properties of the products in the above reactions are considered where appropriate. 2.2 Experimental A l l chemicals used were of reagent grade or comparable p u r i t y and were e i t h e r purchased from commercial s u p p l i e r s or prepared according to reported procedures. Their p u r i t y was ascertained from elemental analyses and/or melting point determinations. melting points were taken in c a p i l l a r i e s i n a i r or under nitrogen using a Gallenkamp Melting Point Apparatus. The uncorrected prepurified A l l solvents were dried according to known methods (12) and thoroughly purged with p r e p u r i f i e d nitrogen p r i o r to use. A l l manipulations, unless otherwise s t a t e d , were performed on the bench (using conventional techniques f o r handling a i r s e n s i t i v e compounds (13)) or in a Vacuum Atmospheres Corporation Dri-Lab model HE-43-2 dry box f i l l e d with p r e p u r i f i e d nitrogen. Infrared spectra were recorded on Perkin Elmer 457 or 71 OA spectrophotometers and c a l i b r a t e d with the 1601 cm" absorption band 1 of a polystyrene f i l m . Proton magnetic resonance spectra were recorded on a Varian Associates T-60 spectrometer using tetramethylsi 1ane as an I: - 6 - i n t e r n a l standard. The l o w - r e s o l u t i o n mass spectra were taken at 70 eV on an A t l a s CH4B spectrometer and the h i g h - r e s o l u t i o n mass spectrum was obtained on an Associated E l e c t r i c a l Industries MS902 spectrometer with the assistance of Dr. G. Eigendorf and Mr. G. Gunn. Elemental analyses were performed by Mr. P. Borda of t h i s Department. Two reagents used frequently throughout t h i s work were n i t r o s y l c h l o r i d e (C1N0) and the bis(triphenylphosphine)iminium halides ((PPhg^NX; X = C l , Br or I ) . 2.2a Preparation of n i t r o s y l Their syntheses are described below. chloride. N i t r o s y l c h l o r i d e was prepared i n the f o l l o w i n g manner, the procedure employed being a m o d i f i c a t i o n of an e a r l i e r report (14). A 100 ml three-necked f l a s k was equipped with a nitrogen i n l e t , a dropping funnel and a drying tower (2 x 20 cm) packed from top to bottom with equal volumes of anhydrous CaClp, KCI and NaN02- The top of the tower was f i t t e d with a 5 ml graduated cold trap equipped with a stopcock on the trap i n l e t , as shown in Figure 1 [ClNO i s a highly c o r r o s i v e substance which necessitates the use of apparatus constructed e x c l u s i v e l y from g l a s s ] . The trap o u t l e t was connected to a 100 ml two-necked f l a s k equipped with a nitrogen i n l e t secured with a s i l i c a gel drying tube. A f t e r f l u s h i n g the e n t i r e apparatus with n i t r o g e n , the reaction f l a s k was charged with concentrated aqueous HC1 (32 ml). An aqueous s o l u t i o n (10 ml) of NaNOp (5.54 g) was added dropwise to the r a p i d l y s t i r r e d a c i d s o l u t i o n at room temperature. The gaseous C1N0 which formed i n s t a n t l y was c a r r i e d by a slow stream of N 7 (ca. 20 ml min ) FIG 1 A P P A R A T U S FOR PURIFYING NITROSYL CHLORIDE - 8 - i n t o the cold trap held at -78°C. ClNO were generated. In t h i s manner, 2.5 ml (50 mmol) of This was d i s t i l l e d under vacuum i n t o the 100 ml f l a s k and 50 ml of C H C T , THF or Et^O were added to the cold ClNO 2 2 to y i e l d deep red s o l u t i o n s which were found to be thermally at 20°C. stable The chemical and physical properties of C1N0 have been e x t e n s i v e l y described (15). All subsequent reactions i n v o l v i n g C1N0 were performed by the dropwise a d d i t i o n of one of these s o l u t i o n s to the appropriate reaction mixture while monitoring the course of the r e a c t i o n by i n f r a r e d spectroscopy. 2.2b Preparation of bis(triphenylphosphine)iminium and i o d i d e , ( P P h J J l X (X = C l , Br or The compounds ( P P h ^ N X I). (X = C l , Br or I) were synthesized according to a modification of a published procedure 2.2bl Preparation of c h l o r i d e , bromide (16). (PPhJpNCl. A three-necked 300 ml f l a s k was equipped with a nitrogen i n l e t , a gas i n l e t , a magnetic s t i r r e r and a Dry-ice r e f l u x condenser secured with a s i l i c a gel drying tube. The f l a s k was charged with PPh 3 (76.8 g , 293 mmol; Matheson Coleman and B e l l ) and chloroethane (100 m l ; Fisher reagent). 1,1,2,2-tetra- The r e s u l t a n t s o l u t i o n was cooled to -78° i n a Dry-ice-isopropanol bath and c h l o r i n e (14.2 g , 200 mmol; Matheson of Canada) was bubbled through the reaction mixture _ over a period of 10 min. 9 - The gas i n l e t was replaced with a stopper and the Dry-ice condenser with a water-cooled r e f l u x condenser. NHpOH-HCl (6.9 g , 100 mmol; M a l l i n c k r o d t a n a l y t i c a l reagent grade) was added and the mixture was allowed to warm to room temperature. F i n a l l y , the r e a c t i o n mixture was heated under r e f l u x u n t i l the evolution of HCl(g) ceased (about 6 h) and then was allowed to cool to room temperature. [Subsequent manipulations were performed i n air.] The orange s o l u t i o n was poured i n t o EtOAc (400 ml) whereupon a large quantity of tan c r y s t a l s formed over a period of 18 h. The c r y s t a l s were c o l l e c t e d by suction f i l t r a t i o n , r e c r y s t a l 1 i z e d from b o i l i n g water and dried i n a vacuum d e s i c c a t o r . d i s s o l v e d i n CH C1 2 The s o l i d was (260 ml) and E t 0 (500 ml) was added, thereby 2 2 producing the white c r y s t a l l i n e product which was c o l l e c t e d by suction filtration. Final drying i n vacuo (5 x 10 49.1 g (85.5 mmol, 85% y i e l d ) of (PPh ) NCl. 3 2 Anal. Calcd. for [ P ( C H ) ] N C 1 : 6 Found: 5 3 2 C, 75.56; H, 5.42; N, 2.22. Proton NMR, r ( i n CDC1 ), - C ^ : 3 2.2b2 mm) at 125°C f o r 70 h afforded C, 75.32; H, 5.27; N, 2.44. m.p. (under N ) : 2 275.5-276.5°C. 2.33(m). Preparation of (PPh-J^NBr. The (PPh ) NBr was prepared in a manner comparable to that 3 2 described above f o r (PPh ) NC1. 2 The required amount of bromine (Fisher reagent grade) was d i s s o l v e d in CHC1 CHC1 2 2 (20 ml) and added dropwise, over a period of 1 h, to the vigorously s t i r r e d r e a c t i o n mixture cooled in an ice-water bath. The i n i t i a l crude product was - 10- obtained by pouring the cooled reaction mixture i n t o E t 0 (600 ml) 2 and was r e c r y s t a l l i z e d from b o i l i n g water (750 ml). The product was f i n a l l y r e c r y s t a l ! i z e d by the a d d i t i o n of EtOAc (500 ml) to a CH^Clg s o l u t i o n (150 ml) of the s a l t . Drying in vacuo (5 x 10 mm) f o r 70 h at 125°C produced 51.0 g (83 mmol, 83% y i e l d ) of the a n a l y t i c a l l y pure (PPh ) NBr. 3 2 A n a l . Calcd. f o r [ P ( C H ) ] N B r : 5 5 Found: 2 C, 69.69; H, 4.92; N, 2.58. Proton NMR, x ( i n CDC1 ), - C H : 3 2.2b3 3 g C, 69.91; H, 4 . 8 9 ; N, 2.26. m.p. (under N ) : 251.0-252.5°C. 2 2.52(m). 5 Preparation of (PPhJoNI. [The f o l l o w i n g manipulations were performed in a i r . ] To a s o l u t i o n of (PPh ) NCl (18.8 g , 32.8 mmol) in EtOH (200 m l , "100%" not 3 2 f u r t h e r p u r i f i e d ) was added f i n e l y pulverized Nal (15.0 g , 100 mmol; M a l l i n c k r o d t a n a l y t i c a l reagent). The mixture was s t i r r e d r a p i d l y 1 h at room temperature and then taken to dryness i_n_ vacuo. product was extracted into a t o t a l of 200 ml of CH C1 2 2 for The and the e x t r a c t was reduced to ca_. 100 ml in vacuo. The addition of E t 0 (300 ml) produced the white 2 crystalline product which was c o l l e c t e d by suction f i l t r a t i o n and dried at 125°C (5 x 10 mm) f o r 70 h. This procedure produced 20.6 g (31.0 mmol, 95% y i e l d ) of a n a l y t i c a l l y pure ( p p h 3 ) N I 2 A n a l . Calcd. f o r [ P ( C g H ) 3 N I : 5 Found: C, 65.09; H, 4.67; N, 2.17. 3 2 g 5 C, 64.97; H, 4 . 5 3 ; N, 2.10. m.p. (under N ) Proton NMR, i-(in CDC1 ), - C H : 2.50(m). 3 • 2 251.0-252.3°C. _ n_ The (PPh ) NX (X = C l , Br or I) compounds 3 2 which are soluble in C H C 1 , CHC^CHC^, EtOH 2 2 i n s o l u b l e in EtOAc, E t 0 , THF, benzene 2 are white s o l i d s and b o i l i n g water, but and hexanes. Although stable i n dry a i r i n d e f i n i t e l y , these compounds are hygroscopic and are therefore best stored in a d e s i c c a t o r . 2.2c Preparation of bis(triphenylphosphine)iminium pentacarbonylhalotungstates, (PPh ) NW(C0) X (X = C l , Br or 3 2 I). 5 These complexes were conveniently prepared by the reaction of W(C0) with the appropriate (PPh ) NX s a l t . 6 3 2 The experimental procedure, using the iodide complex as a representative example, was as f o l l o w s . A DME (90 ml) s o l u t i o n containing W(C0) (7.39 g, 21.0 mmol; 6 Pressure Chemical Co.) and (PPh ) NI (13.3 g , 20.0 mmol) was heated under 3 r e f l u x for 6 h. 2 The r e s u l t a n t c l e a r yellow s o l u t i o n was allowed to cool to room temperature and the volume reduced in vacuo u n t i l the f i r s t traces of c r y s t a l s appeared. Slow a d d i t i o n of hexanes (120 ml) produced yellow c r y s t a l s which were c o l l e c t e d by suction f i l t r a t i o n and washed with hexanes (2 x 40 ml). f o r 18 h. The product was d r i e d at 60°C (5 x 10 mm) A q u a n t i t a t i v e y i e l d of a n a l y t i c a l l y pure (PPh ) NW(C0) I 3 was thus obtained (Table 2 5 I). The (PPh ) NW(C0) X (X = Cl or Br) complexes were s i m i l a r l y 3 2 5 obtained in greater than 95% y i e l d s and t h e i r elemental analyses and physical properties are compiled in Table I. Table I. Compound Elemental Analyses and Physical Properties of (PPh ) NW(C0) X (X = C l , Br or 3 Color Analyses, % Mp. ,°C (under N ) C H I Calcd: 54.84 3.37 1.56 Found: 54.44 3.51 1.38 Calcd: 52.25 3.21 1.49 Found: 52.04 3.31 1.33 2 (PPh ) NW(C0) Cl 3 2 5 (PPh ) NW(C0) Br 3 2 5 Yellow Yellow 145(dec) 150(dec) 2 5 Proton NMR, T(in CDClJ " 6 5 C H 2.52(m) I). -1 v ( C 0 ) , cm (in CH C1 ) 2 2 2065(w), 1915(s), 1837(m) 2.50(m) 2065(w), 1915(s), 1842(m) ro (PPh ) NW(C0) I 3 2 5 Yellow 178(dec) Calcd: 49.77 3.06 1.42 Found: 49.74 3.20 1.22 2.51(m) 2063(w), 1918(s), 1850(m) i - 13 - A l l three complexes are yellow s o l i d s which may be exposed to a i r for several days without noticeable decomposition but are best stored under n i t r o g e n . They are very s o l u b l e in C r ^ C ^ , diglyme DME, less soluble in Et^O, THF and EtOAc and and i n s o l u b l e in hexanes. The s o l u b i l i t y increases markedly with i n c r e a s i n g atomic weight of the halogen. 2.2d Reactions of n i t r o s y l c h l o r i d e with some anionic and neutral complexes of manganese, rhenium and i r o n . Reaction with bi s (triphenylphosphine)imini um pentacarbonylmanganate, (PPh,,),,NMn (CO) To a l i g h t yellow s o l u t i o n of (PPh ) NMn(C0) (17) (0.81 g , 3 1.1 mmol) in CH C1 2 2 2 5 (30 ml) was added dropwise with s t i r r i n g at room temperature a s o l u t i o n of ClNO i n C H C 1 . 2 2 Immediately, the reaction s o l u t i o n became deep red and gas was evolved. A f t e r the a d d i t i o n of ClNO was complete, the s o l u t i o n was s t i r r e d f o r an a d d i t i o n a l 10 min. D i s t i l l a t i o n in vacuo y i e l d e d a CH^Cl^ s o l u t i o n containing only Mn(C0) (N0) which was i d e n t i f i e d by i t s i n f r a r e d spectrum (18). 4 The y i e l d was estimated to be 70% from the r e l a t i v e i n t e n s i t i e s of the carbonyl absorptions i n the reactant and product i n f r a r e d s p e c t r a . The reactions of C1N0 with some organometallic complexes of rhenium and iron were performed s i m i l a r l y and the experimental procedures are summarized in Table II. Table II. T r a n s i t i o n metal compd. (mmol) Na[Re(C0) ] (4.0) 19 I; Reaction of N i t r o s y l Chloride with some Complexes of Rhenium and Iron. Amt. of C1N0 (mmol) 4.0 Solvent (ml) THF(50) Temp, and reaction time 0 ° , 15 min. Products(yields) Re (C0) 2 I s o l a t i o n and Identification Sublimation at 40-60° 1Q infrared spectrum Ph SnRe(C0)5°(1.5) 3 2.0 CH C1 (10) 2 2 20°, 15 min. Re(C0) SnCl Ph _ 5 x 3 x (x = 0,1,2,3) Na [Fe(C0) ] ' (10) 20 Et 0(150) ,24 Na[CpFe(C0) ]"(14) 14 THF(50) 2 1 2 2 2 4 2 9 - 7 8 ° , 30 min. 0°,. 20 min. Sublimation at 60° infrared spectrum* [CpFe(C0) ] M0%) Identification 2 2 (5xl0 mm): 2 3 3.0 CrLCl (15) ? 20°, 15 min. CpFe(C0) 9 x 3-x (x = 0,1,2,3) S n C 1 P h THF e x t r a c t s ; . 25 spectrum a. By comparison with the i n f r a r e d spectrum of the authentic compound. b. Inferred from the c h a r a c t e r s t i c s h i f t of the carbonyl absorptions to higher wave numbers. infrared in s o l u t i o n by infrared spectroscopy 24, CpFe(C0) SnPh (2.0). -,j 3 Vacuum d i s t i l l a t i o n ; 23 spectrum 9 J 9 Fe(C0) (N0) (30%) 9 (5xlO" mm); 9 infrared - 15 - 2.2e Reactions of n i t r o s y l c h l o r i d e with t r i c a r b o n y l ( n - c y c l o p e n t a 5 d i e n y l ) anions of chromium, molybdenum and tungsten, [CpM(C0) ]~ 3 (M = C r , Mo or W). A THF s o l u t i o n of C1N0 was added dropwise, with r a p i d stirring at room temperature to Na[CpCr(C0) ] (27) (4.89 g , 22.0 mmol) in THF 3 (120 m l ) . Gas was evolved and a dark s o l i d p r e c i p i t a t e d during the course of the r e a c t i o n . The a d d i t i o n of C1N0 was continued u n t i l the s t a r t i n g anion was completely consumed. The i n f r a r e d spectrum of the f i n a l reaction mixture revealed the presence of CpCr(C0) (N0) (1) and 2 [CpCr(C0) ] 3 2 (28) as the major carbonyl-containing compounds. The mixture was taken to dryness i n vacuo and sublimation of the residue at 60° (5 x 10 mm) onto a water-cooled probe produced 1.01 g (5.0 mmol, 23% y i e l d ) of CpCr(C0) (N0) which was. i d e n t i f i e d by i t s 2 spectrum. infrared The reactions of the molybdenum and tungsten containing anions proceeded s i m i l a r l y . If an excess of C1N0 was employed i n the above syntheses, s i g n i f i c a n t amounts of CpM(N0) Cl and attendant 2 decomposition products were formed. The physical and chemical properties of the CpM(C0) (N0) complexes have been previously described (28). 2 2.2f Reaction of sodium n i t r i t e and a c e t i c a c i d with sodium t r i c a r b o n y l ( n - c y c ! o p e n t a d i e n y l ) t u n g s t a t e , Na[CpW(C0) ]. 5 3 To a s o l u t i o n of Na[CpW(C0) ] (27) (1.80 g , 5.1 mmol) and 3 NaN0 2 (0.35 g , 5.1 mmol) i n nitrogen-saturated water (30 ml) was added dropwise with s t i r r i n g an aqueous s o l u t i o n (10 ml) of a c e t i c a c i d (5 mmol). Immediately, gas was evolved and a dark yellow s o l i d formed. The reaction - 16 - mixture was f u r t h e r s t i r r e d for 0.5 h and then f i l t e r e d . s o l i d was d r i e d in vacuo and sublimed at 60°C (5 x 10 The r e s u l t a n t mm) onto a water-cooled probe producing 1.01 g of a mixture of CpW(C0) (N0) and 2 CpW(C0) H which were i d e n t i f i e d by t h e i r i n f r a r e d spectra (1, 27, 29). 3 2.2g Reactions of n i t r o s y l c h l o r i d e with bis(triphenylphosphine)iminium pentacarbonylhalotungstates, (PPh ) NW(C0) X (X = C l , Br or 3 2 5 I), and with tetraethylammonium pentacarbonylchloro (or methyl) tungstate, Et NW(C0) X (X = Cl or Me). 4 5 A C h ^ C ^ s o l u t i o n of C1N0 was added dropwise with s t i r r i n g (PPh ) NW(C0) Br (5.5 g , 5.8 mmol) in CH C1 3 2 5 2 2 (50 ml) at -78°C. to Gas was evolved and the a d d i t i o n of C1N0 was continued u n t i l the carbonyl i n f r a r e d absorptions due to the s t a r t i n g material disappeared. mixture was taken to dryness in vacuo. 45°C (5 x 10 The Sublimation of the residue at mm) onto a water-cooled probe produced 0.82 g (2.0 mmol, 35% y i e l d ) of W(C0) (N0)Br which was i d e n t i f i e d by i t s 4 infrared spectrum (30). The reactions of ClNO with the remaining tungsten complexes were performed s i m i l a r l y and the experimental d e t a i l s are presented i n Table 2.2h III. Reactions of t e t r a c a r b o n y l h a l o n i t r o s y l t u n g s t e n s , W(C0) (N0)X 4 (X = Cl or Br), with t e t r a h y d r o f u r a n . A THF s o l u t i o n (20 ml) containing W(C0) (N0)C1 (0.50 g, 4 1.4 mmol) was s t i r r e d at room temperature u n t i l the i n f r a r e d absorptions Table III. Reactions of N i t r o s y l Chloride with (PPh ) NW(C0) X (X = C l , Br or 3 2 5 I) and Et NW(C0) X (X = Cl or Me). 4 Metal Complex (mmol) Solvent (ml) Reaction temp. (PPh ) NW(C0) Cl(5.1) CH C1 (50) -78° W(C0) (N0)C1(25%) A (PPh ) NW(C0) BY(5.8) CH C1 (50) -78° W(C0) (N0)Br(35%) A (PPh ) NW(C0) I(9.O) CH C1 (50) -78° W(CO) (NO)I(2535) A Et NW(C0) Cl THF(75) or -78° W(C0) and CH C1 (100) 25° 3 3 3 4 2 5 2 5 2 5 (7.7) 31 5 2 2 2 2 Et NW(C0) CH (3.6) 2 4 5 3 2 2 2 2 CH C1 (50) 2 2 -78° or 25° Products(yields) 4 4 4 g W(C0) (N0)C1 (<v8%) W(C0) , W(C0) (N0)C1, 6 4 Sublimation at 45°C (5x10" mm), i n f r a r e d spectrum. B I d e n t i f i c a t i o n in s o l u t i o n by i n f r a r e d spectroscopy. A 4 4 Et NW(C0) Cl A I s o l a t i o n and Identification 5 B i - 18 - due to the i n i t i a l reactant disappeared (ca. 24 h). taken to dryness in vacuo (5 x 10 The s o l u t i o n was mm) to give a q u a n t i t a t i v e y i e l d of an orange complex i d e n t i f i e d as •[W(C0) (N0)(THF)C1] . 2 2 A n a l . Calcd. for W(C0) (N0)C1(C Hg0): 2 N, 3 . 7 1 ; C l , 9.39. v(C0) cm" 1 Found: (in THF): 4 C, 19.10; H, 2 . 1 2 ; C, 19.20; H, 2 . 1 1 ; N, 3.56; C l , 9.64. 2020(s); 1907(s). Proton NMR, ( i n CgDg), THF: v(N0) cm" (in THF): 1 1636(s). 5.60(m); 7.85(m). T S i m i l a r l y , W(C0) (N0)Br was q u a n t i t a t i v e l y converted to 4 [W(C0) (NO)(THF)Br] 2 as evidenced by the s i m i l a r i t y of i t s 2 spectrum with that of v(C0) cm" [W(C0) (N0)(THF)C1] . 2 2 (in THF): 1 infrared 2010(s); 1905(s). v(N0) cm" 1 (in THF): 1635(s). The [W(C0) (N0)(THF)X] 2 2 (X = C l o r B r ) complexes are y e l l o w - orange s o l i d s which are stable in a i r f o r at l e a s t 10 h but are best stored under n i t r o g e n . i n s o l u b l e in hexanes. They are soluble i n THF, CH C1 2 2 and benzene and However, s o l u t i o n s containing these compounds decompose r a p i d l y upon exposure to a i r . 2.3 2.3a Results and Discussion Bis(triphenylphosphine)iminium c h l o r i d e , bromide and i o d i d e , ( P P h J N X (X = C l , Br or 2 I). The (PPh ) NX (X = Cl or Br) compounds can best be prepared 3 2 in high y i e l d s according to eq. 1. - 19 - 3PPh + 2X + NH 0H-HC1 3 2 2 ° - ( P P h ^ N X + Ph PO + HC1 + 3HX 1. 3 This synthesis has been previously u t i l i z e d only in the preparation of (PPh ) NCl (16), but we have subsequently found that the above reaction 3 2 can also be d i r e c t l y applied to the high y i e l d synthesis of (PPh^NBr. This method, however, f a i l s f o r the preparation of ( P P h ) N I . 3 2 The l a t t e r compound i s conveniently obtained q u a n t i t a t i v e l y by the d i s p r o p o r t i o n a t i o n reaction between (PPh ) NCl and Nal in ethanol 3 2 according to the equation (PPh ) NCl + Na + I" 3^- (PPh ) NI + NaCl(s) + 3 2 3 2. 2 i n which the e q u i l i b r i u m l i e s well to the side of ( P P h ^ N I by v i r t u e of the low s o l u b i l i t y of NaCl in ethanol. The syntheses of (PPh ) NX 3 2 (X = Br or I) have been previously reported although a cumbersome and i n e f f i c i e n t method was used (16). The (PPh ) NX compounds are stable i n d e f i n i t e l y in a i r and 3 water. 2 However, contrary to a previous report (16), we f i n d them to be quite hygroscopic as shown by elemental analyses and proton NMR spectroscopic i n v e s t i g a t i o n s . i s detrimental Consequently, i f the presence of water in subsequent reactions i n v o l v i n g these s a l t s , they must be stored in a d e s i c c a t o r . The compounds are thermally s t a b l e even at t h e i r r e l a t i v e l y high melting points which are in excess of 250°C. chemical and physical properties are not u n l i k e those of Their tetraethyl- ammonium s a l t s except t h a t , s u r p r i s i n g l y , the (PPh ) NX compounds are 3 very soluble in c h l o r i n a t e d s o l v e n t s . 2 The geometric and e l e c t r o n i c - 20 - structures of the [ ( P P h ) N ] 3 T 2 cation have been the subjects of considerable study and both a bent and l i n e a r arrangement of P-N-P atoms have been found (33, 34). The use of [ ( P P h ) N ] 3 2 + as a counterion in the i s o l a t i o n of t r a n s i t i o n metal carbonyl anions i s of immense value. Not only are c r y s t a l l i n e samples of the carbonyl anions r e a d i l y o b t a i n a b l e , but these s a l t s are often a i r stable in the s o l i d state f o r many hours. A l s o , unlike the a l k a l i metal s a l t s of carbonyl anions, the [ ( P P h ) N ] 3 d e r i v a t i v e s are very soluble and stable i n c h l o r i n a t e d s o l v e n t s . + 2 In f a c t , t h i s enhanced s t a b i l i t y has been highly b e n e f i c i a l i n the x-ray s t r u c t u r a l determinations of many i n t e r e s t i n g mono- and p o l y - n u c l e a r metal carbonyl complexes (33). 2.3b Bis(triphenylphosphine)iminium pentacarbonylhalotungstates, (PPh ) NW(C0) X (X = C l , Br or 3 2 5 I). The (PPh ) NX (X = C l , Br or I) s a l t s react with W(C0) 3 2 r e f l u x i n g DME with the evolution of gas to give v i r t u a l l y g in quantitative y i e l d s of the (PPh ) NW(C0) X complexes, as i n eq. 3. 3 2 (PPh ) NX + W(C0) 3 2 g 6 (PPh ) NW(C0) X + CO 3 2 5 3. These syntheses are comparable to those reported f o r the preparation of the Et NW(C0) X complexes i n diglyme at 120°C (31). 4 5 However, the reactions reported here are performed with great f a c i l i t y at 85°C and are complete in s i x hours. The lower reaction temperature and the shorter reaction _ 21 _ time serve to eliminate any accompanying decomposition products which may a r i s e from the p y r o l y s i s of the desired m a t e r i a l s . Unlike the Et NW(C0) X compounds, the [ ( P P h ) N ] 4 5 3 + 2 derivatives are not p h o t o l y t i c a l l y decomposed by ordinary l i g h t i n g , and they are also more stable toward atmospheric o x i d a t i o n . In f a c t , as s o l i d s they are stable in a i r f o r several days and t h e i r s o l u t i o n s may be exposed to a i r f o r a short period of time without noticeable decomposition. In c o n t r a s t , the [Et^N]" " containing compounds are so 1 unstable i n s o l u t i o n that the a c q u i s i t i o n of c o n s i s t e n t l y accurate i n f r a r e d data i s d i f f i c u l t . The s o l u t i o n i n f r a r e d spectra of the (PPh ) NW(C0) X 3 2 5 complexes d i s p l a y the expected three-band pattern s i m i l a r to the i s o structural neutral compounds Mn(C0)gX (X = C l , Br or I) W(C0)^L (L = amine or phosphine) (36)-. (35) and Of course, the C-0 s t r e t c h i n g frequencies of the i o n i c species occur at much lower frequencies due to the enhanced metal-carbonyl backbonding. Because of t h e i r greater s o l u b i l i t y in common organic s o l v e n t s , the [ ( P P h ) N ] 3 + 2 s a l t s are more useful than the [Et^N]" " analogs 1 as r e a c t i v e synthetic precursors (17, 37-40). In p a r t i c u l a r , they can be r e a d i l y converted to the W(C0) (N0)X (X = C l , Br or I) complexes as 4 described subsequently. In summary i t should be noted that a wide v a r i e t y of (PPh ) NM(C0) X complexes, where X i s a halogen or pseudo3 2 5 halogen, have been previously prepared by diverse means (37-41). However, the preparative methods described in t h i s t h e s i s are f a r superior simply because the desired products are obtained much more - 22 - conveniently and i n q u a n t i t a t i v e 2.3c Reactions of n i t r o s y l It yields. c h l o r i d e with metal carbonyl anions. is a well known f a c t that t r a n s i t i o n metal carbonyl anions are s u f f i c i e n t l y n u c l e o p h i l i c to d i s p l a c e a halide from both organic and inorganic halides according to the general reaction scheme Cp M(C0) R + X [Cp M(C0) ]" + RX m m n 4. n where m = 0 or 1; n = 1-5 depending on M (11). The success of the above reaction i s dependent, among other v a r i a b l e s , on the n u c l e o p h i 1 i c i t y of the a n i o n , and the rate of such a reaction has been used as a measure of the n u c l e o p h i l i c strength of some metal carbonyl anions (42). In a conversion analogous to the above reaction we f i n d that some of these anions w i l l also d i s p l a c e the c h l o r i d e from n i t r o s y l c h l o r i d e thereby providing a convenient synthetic route to neutral nitrosyl compounds. The method can a-lso be applied to the d i - a n i o n i c complex,[Fe(C0) ] ". Except f o r the preparation of 2 4 (RB(pz) = t r i s ( p y r a z o y l ) b o r a t e ; 3 [(RB(pz) )M(C0) ]" 3 ignored. (RB(pz) )M(C0) (N0) 3 2 R = H or p z ; M = C r , Mo or W) from (10), t h i s c l a s s of reactions has l a r g e l y been 3 Typical examples of such reactions are summarized in eq. 5-8. (PPh ) NMn(C0) + C1N0 3 2 5 N a [ F e ( C 0 ) ] + 2C1N0 2 3 (M = C r , Mo or W) 4 Fe(C0) (N0) 4 Na[CpM(C0) ] +C1N0 • Mn(C0) (N0) 2 THF * ~ CpM(C0) (N0) 2 2 5. 6. 7. - 23 - THF or CH C1 9 A[W(C0) X] + C1N0 L 5 (A = ( P P h ) N ; 3 2 L 9 *~ W(C0) (N0)X 8. 4 X = C l , Br or I: A = Et^N; X = Cl or Me) A l l these conversions are accompanied by gas evolution and they proceed r e a d i l y i n reasonable y i e l d s . The attendant formation of an inorganic c h l o r i d e undoubtedly provides a strong thermodynamic driving force f o r these r e a c t i o n s . It appears that n i t r o s y l c h l o r i d e behaves as a nitrosonium s a l t in i t s reactions with anions even though the molecule i t s e l f bent and the N-Cl bond i s l a r g e l y covalent. is For i n s t a n c e , microwave spectroscopy of i s o t o p i c a l l y l a b e l l e d ClNO molecules shows the 0-N-C1 angle to be 113.3° (43), and an N-0 bond order of 1.9 i s obtained from force constant c a l c u l a t i o n s u t i l i z i n g i n f r a r e d data (15). Furthermore, the N-0 s t r e t c h i n g frequency of C1N0 i n a dichloromethane s o l u t i o n occurs at 1845 cm" while i n nitrosonium s a l t s , which contain the t r i p l y bonded 1 nitrosonium c a t i o n , the values f a l l w i t h i n the 2150-2400 c m These observations therefore suggest that the n i t r o s y l ? i s mainly covalent containing an sp double bond. -1 range (44). c h l o r i d e molecule hybridized nitrogen atom and an N-0 Nevertheless, the anomalously large N-Cl distance of O 1.975 ± 0.005 A (43) has been explained in terms of the of i o n i c resonance forms such as 0= [:O=N:] CI + contribution - 24 - In the gaseous s t a t e , at 20°C, n i t r o s y l NO and C l 2 to the extent of about 0.5% (44). c h l o r i d e disproportionates Although the extent of t h i s e q u i l i b r i u m in s o l u t i o n s of dichloromethane or tetrahydrofuran not known, evidence f o r i t i s presented i n Chapter IV. is Chemically, n i t r o s y l c h l o r i d e often behaves as a strong o x i d i z i n g agent, being reduced to C l " and NO or N 2.3cl (15, 45, 46). 2 Reactions of n i t r o s y l c h l o r i d e with organometallic anions of manganese, rhenium and i r o n . The reaction of n i t r o s y l c h l o r i d e with (PPh^^NMn(C0) g in dichloromethane proceeds smoothly and c l e a n l y at room temperature to give Mn(C0) (N0) i n good y i e l d s . However, the analogous reaction 4 involving Na[Re(C0) ] affords R e ^ C O ) - ^ as the only carbonyl containing compound. g It appears that the [Re(C0) ]~ anion i s o x i d i z e d to the dimer by g n i t r o s y l c h l o r i d e according to eq. 9. Na[Re(C0) ] +.C1N0 5 yte (C0) 2 1 0 + NaCl + NO 9. In t h i s connection the use of n i t r o s y l c h l o r i d e as an oxidant has already been mentioned and indeed, nitrosonium s a l t s have been used p r e v i o u s l y i n the oxidation of organometallic anions. An example of such an oxidation i s the formation of the paramagnetic C r ( C 0 ) I complex as g indicated i n eq. 10 (45). [ C r ( C 0 ) I ] " + NOPFg 5 C r ( C 0 ) I + P F " + NO 5 g 10. to - 25 - The d i a n i o n i c N a [ F e ( C 0 ) ] complex reacts with n i t r o s y l 2 4 c h l o r i d e to form F e ( C 0 ) ( N 0 ) as the only n i t r o s y l containing species. 2 2 The p o s s i b i l i t y that t h i s reaction proceeds through the well known [Fe(C0) (N0)]~ anion was not i n v e s t i g a t e d i n our work. 3 However, the i n f r a r e d spectrum of the f i n a l reaction mixture confirms the presence of small amounts of F e ( C 0 ) - | , l i k e l y produced by the n i t r o s y l 3 chloride 2 o x i d a t i o n of [ F e ( C 0 ) ] 4 . This i s not s u r p r i s i n g i n l i g h t of the f a c t that a s i m i l a r oxidation of [HFe(C0) ] 4 an important synthetic route to F e ( C 0 ) 3 by manganese dioxide c o n s t i t u t e s 1 2 (29, 47, 48). The r e l a t i v e n u c l e o p h i l i c i t i e s of a v a r i e t y of metal carbonyl and cyclopentadienylmetal carbonyl anions, i n the presence of Bu^NClO^, have been compiled and the f a c t o r s which determine n u c l e o p h i l i c character have been discussed (42). The reactions of n i t r o s y l chloride with the anions described in t h i s chapter suggest a r e l a t i o n s h i p between the r e a c t i o n products and the n u c l e o p h i l i c i t y of the anions. Hence, the m i l d l y n u c l e o p h i l i c [Mn(C0)g]~ anion r e a d i l y y i e l d s Mn(C0) (N0) while the 4 more n u c l e o p h i l i c [Re(CO)^] Re (C0).|Q. anion simply gives the o x i d a t i o n product, Not s u r p r i s i n g l y t h e r e f o r e , the most n u c l e o p h i l i c anion thus 2 f a r i n v e s t i g a t e d , [CpFe(C0) ]~> i s o x i d i z e d nearly q u a n t i t a t i v e l y 2 to [CpFe(C0) l . 2 2 In an e f f o r t to reduce the n u c l e o p h i l i c behavior of [Re(C0)g] and-[CpFe(C0) ] 2 the Ph^Sn d e r i v a t i v e s of these anions were prepared. G e n e r a l l y , complexes of the type Ph^SnM, where M i s a t r a n s i t i o n metal carbonyl moiety, contain a predominantly covalent tin-metal bond. Consequently, i t i s not unreasonable that the t r a n s i t i o n metal carbonyl - 26 - group w i l l possess a g r e a t l y reduced n u c l e o p h i l i c i t y . However, the subsequent reactions of n i t r o s y l c h l o r i d e with Ph SnRe(C0) 3 CpFe(C0) SnPh 2 5 and in dichloromethane y i e l d only the mixed R e ( C 0 ) S n C l P h _ 3 5 and C p F e ( C 0 ) S n C l P h _ 2 x 3 x complexes, where x = 1, 2 or 3. the tin-carbon bond rather than the tin-metal x 3 x The cleavage of bond p a r a l l e l s the reactions of halogens and hydrogen halides with Ph SnMn(C0) , Ph SnRe(C0) , and 3 CpFe(C0) SnPh 2 5 3 5 (24, 49-51). 3 The success of the reaction of n i t r o s y l c h l o r i d e with (PPh ) NMn(C0) 3 2 5 prompted the attempted i s o l a t i o n of the [ R e ( C 0 ) ] " and 5 [CpFe(C0) ]~ anions as t h e i r [ ( P P h ) N ] 2 3 + 2 salts. Unfortunately, all e f f o r t s were thwarted by the p e r s i s t e n t formation of Re (C0)-jQ, 2 [CpFe(C0) ] 2 and attendant decomposition products. 2 Even though [Mn(C0)g] and HMn(C0) react with Diazald to y i e l d Mn(C0) (N0) (18), the same 5 4 reaction could not be effected with e i t h e r [Re(C0) ]~ and [CpFe(C0) ]~ 5 or t h e i r respective hydrido d e r i v a t i v e s . reason f o r t h e i r inherent i n s t a b i l i t y While there i s no 4 Reactions of n i t r o s y l a priori under ambient c o n d i t i o n s , the Re(C0) (N0) and CpFe(C0)(N0) complexes s t i l l 2.3c2 2 c h l o r i d e with remain unknown. tricarbonyl(n -cyclopentadienyl) 5 anions of chromium, molybdenum and tungsten, [CpM(C0) ]~ 3 (M = C r , Mo or W). Treatment of Na[CpM(C0) ] with n i t r o s y l 3 chloride in t e t r a - hydrofuran y i e l d s a mixture of the CpM(C0) (N0), CpM(N0) Cl and [ C p M ( C 0 ) l 2 compounds. 2 Even though the anions of chromium and molybdenum are 3 slightly 2 - 27 - less n u c l e o p h i l i c than [Mn(C0)g]~ (42), a s i g n i f i c a n t amount of oxidation to [CpM(C0) ] occurs. 3 The formation of CpM(N0) Cl a r i s e s from the 2 2 o x i d a t i v e s u b s t i t u t i o n of n i t r o s y l c h l o r i d e on the i n i t i a l CpM(C0) (N0) 2 products according to eq. 1 1 . CpM(C0) (N0) + C1N0 «~ CpM(N0) Cl + 2C0 2 11. 2 (M = C r , Mo or W) This i s a p a r t i c u l a r example of the broad c l a s s of reactions between n i t r o s y l c h l o r i d e and neutral metal carbonyl complexes to be discussed i n Chapters III and IV. The preparation of F e ( C 0 ) ( N 0 ) by the treatment of 2 2 Na[Fe(C0) N0] or Na[Fe(C0) H] with aqueous sodium n i t r i t e and a c e t i c a c i d 3 4 has been previously reported (52, 53). The reaction of Na[CpW(C0) ] 3 with these reagents proceeds analogously whereupon a mixture of CpW(C0) (N0) and CpW(C0) H i s formed. 2 3 The l a t t e r complex i s undoubtedly produced by the d i r e c t protonation of [CpW(C0) ]~ by a c e t i c a c i d , a well 3 known synthesis (27). However, d i f f i c u l t y in separating these two products renders t h i s synthetic route i m p r a c t i c a l . The very high y i e l d syntheses of a l l three CpM(C0) (N0) complexes developed during the course 2 of t h i s work are d e t a i l e d in Chapter IV. - 28 - 2.3c3 Reactions of n i t r o s y l c h l o r i d e with iminium pentacarbonylhalotunqstates, bis(triphenylphosphine)(PPhp)QNW(C0)^X (X = C l , Br or I) and tetraethylammonium pentacarbonylchloro (or methyl) tungstate, Et NW(C0) X ( X = C l o r M e ) . 4 5 A l l three (PPh ) NW(C0)gX complexes react with n i t r o s y l 3 2 c h l o r i d e i n dichloromethane at -78°C to give moderate y i e l d s of W(C0) (N0)X according to eq. 12. 4 ( P P h ) N W ( C 0 ) X + C1N0 3 2 5 If excess n i t r o s y l c h l o r i d e i s used, *-W(C0) (N0)X + ( P P h ^ N C l + CO 12. 4 or i f the reaction i s attempted at room temperature, the y i e l d s of the desired products are reduced markedly. The W(C0) (N0)X complexes have been previously synthesized by 4 the action of p-toluenesulphonic acid and p e n t y l n i t r i t e , gensulfate acid on Et NW(C0)^X (30). 4 or nitrosonium hydro- Our repeated attempts to obtain the desired products i n y i e l d s which even approximate those reported met with f a i l u r e . Another reported route to the c h l o r i d e and iodide containing compounds involves the treatment of HW (C0)g(NO) with n i t r o s y l 2 c h l o r i d e and iodine r e s p e c t i v e l y (54). However, the required HW (C0)g(N0) complex can be obtained from a two-step synthesis i n y i e l d s 2 of only 40% (55, 56). Unlike a l l of the previous syntheses discussed above, the present reactions of n i t r o s y l c h l o r i d e with (PPh ) NW(C0)gX a f f o r d the 3 2 W(C0) (N0)X complexes without the attendant formation of W(C0)g. 4 Thus, the d i f f i c u l t task of separating the p h y s i c a l l y s i m i l a r W(C0) (N0)X 4 and W(C0) compounds i s avoided. fi A l s o , since the (PPh,) NW(C0) X 9 R - 29 - complexes are r e a d i l y obtained in q u a n t i t a t i v e y i e l d , as discussed e a r l i e r i n t h i s chapter, t h i s preparative route i s indeed a t t r a c t i v e . I n t e r e s t i n g l y , the choice of countercation i n the reactions between the [W(C0)gX] s a l t s and n i t r o s y l c h l o r i d e has a profound e f f e c t on product d i s t r i b u t i o n . Unlike the [ ( P P h ^ N ] * s a l t s , the Et NW(C0) X compounds r e a d i l y y i e l d W(C0)g as the major product regard4 5 less of the solvent employed. Et NW(C0)gMe, when treated with n i t r o s y l c h l o r i d e in d i c h l o r o 4 methane, produces a mixture of W(C0) (N0)C1, W(C0) and Et NW(C0) Cl. 4 6 4 5 The l a t t e r compound i s l i k e l y formed in a manner s i m i l a r to the reaction of hydrogen c h l o r i d e with Me NW(C0) R, where R = Me or CHpPh. 4 g For example, treatment of Me^VKCO^CHpPh with a s l i g h t excess of hydrogen c h l o r i d e y i e l d s toluene (94%) and Me NW(C0) Cl (32). 4 5 Once the primary product, Et NW(C0)gCl, i s formed, subsequent reaction with 4 n i t r o s y l c h l o r i d e produces W(C0) (N0)C1 and W(C0)g as previously 4 described. In support of t h i s reaction pathway i t was found that an excess of n i t r o s y l c h l o r i d e simultaneously reduced the f i n a l y i e l d of Et NW(C0) Cl and increased the y i e l d s of W(C0) (N0)C1 and W(C0) . 4 5 4 g The a n t i c i p a t e d product from the reaction between n i t r o s y l c h l o r i d e and Et NW(C0) Me was the as yet unknown W(C0) (N0)Me complex. 4 5 4 This type of conversion i s not without precedent since the anions [R M'M(C0) ]~ 3 g (M = Mo or W; M' = S i , Ge, Sn or Pb; R = Me or Ph) react with NOPFg to give R M'M(C0) (N0) i n y i e l d s ranging from 7 to 74% ( 4 6 i ) . 3 4 Our attempts to prepare W(C0) (N0)Me by the a c t i o n of methyl Grignard 4 reagents, methyl l i t h i u m and trimethylaluminum on W(C0) (N0)X complexes /l - 30 - f a i l e d , probably due to the great l a b i l i t y of the carbon monoxide ligand in the halo-containing reactant. 2.3d Reactions of t e t r a c a r b o n y l h a l o n i t r o s y l t u n g s t e n s , W(C0) (.N0)X 4 (X = Cl or B r ) , with tetrahydrofuran. The f a c i l e s u b s t i t u t i o n of e i t h e r one or two carbonyl ligands i n W(C0) (N0)X (X = C l , Br or I) has been amply demonstrated (57, 58). 4 For example, reaction with s t o i c h i o m e t r i c q u a n t i t i e s of e i t h e r PPh^ or AsPhg i n r e f l u x i n g chloroform y i e l d s mer-W(C0),,(N0) (L)X, whereas excess ligand produces c j ^ s - W t C O ^ N O H L ^ X . If carbonyl s u b s t i t u t i o n is effected using bis(diphenylarsino)methane (dam) only the monodentate mer_-W(C0) (N0)(dam)X and cis-W(C0) (NQ)(dam)pX complexes are formed. 3 2 However, when h a l f the s t o i c h i o m e t r i c amount of dam i s employed, the product obtained i s [ W t C O ^ N O ^ ^ d a m , which i s believed to contain both halide and dam bridges (58). We discovered that s t i r r i n g a tetrahydrofuran s o l u t i o n of W(C0) (N0)X (X = Cl or Br) for 24 hours r e s u l t e d i n the 4 quantitative formation of the corresponding [W(C0) (NO.) (THF)X] complexes. 2 2 The presence of tetrahydrofuran in these compounds was confirmed by elemental analyses and proton NMR spectroscopy which displayed the c h a r a c t e r i s t i c proton resonances at x5.60(m) and x7.85(m). As expected, these values are somewhat lower than the corresponding values of uncomplexed tetrahydrofuran. The e l e c t r o n donation from the THF oxygen atom to the central metal i s expected to d e s h i e l d the protons on the a-carbon more than those on the 3-carbon atoms. In agreement with t h i s - 31 - e x p e c t a t i o n , the a-carbon proton resonances do indeed experience the greater downfield shift. The [w^CO^NO) ( T H F j X ^ complexes are believed to be dimeric with structures s i m i l a r to that proposed f o r [W^O^NCOXlgdam except that the bridging dam i s replaced by two t e r m i n a l l y bonded tetrahydrofuran l i g a n d s , as shown by two p o s s i b l e structures A and B. A Consistent B with t h i s b e l i e f , both the tetrahydrofuran and dam containing compounds d i s p l a y s i m i l a r i n f r a r e d spectra which are c h a r a c t e r i z e d by two carbonyl and one n i t r o s y l s t r e t c h i n g absorptions (58). In compliance with the "18-electron r u l e " , the dimers presumably are held together by halide bridges without the aid of a metal-metal bond. - 32 - CHAPTER III REACTIONS OF NITROSYL CHLORIDE WITH NEUTRAL METAL CARBONYL COMPLEXES 3.1 Introduction As described i n the previous chapter the reactions of nitrosyl halides with metal carbonyl or n -cyc1opentadieny1metal carbonyl anions 5 had received v i r t u a l l y no a t t e n t i o n u n t i l t h i s study. On the other hand, t h e i r reactions with neutral complexes have been p r e v i o u s l y i n v e s t i g a t e d , although by no means exhaustively (9). n i t r o s y l halides are powerful Because the o x i d a n t s , s t r i c t a t t e n t i o n must be given to the r e a c t i o n conditions which a r e , by and l a r g e , e m p i r i c a l l y determined. Thus the temperature, the s o l v e n t , the phase and e s p e c i a l l y the stoichiometry of the reaction are c r u c i a l i n determining the r e a c t i o n products. Reactive substrates include non-carbonyl as well as carbonyl containing compounds. In the former category, the n i t r o s y l halides u s u a l l y add o x i d a t i v e l y to the metal complex with or without ligand displacement. However, the majority of the published reports describe the reactions of n i t r o s y l halides with t r a n s i t i o n metal complexes which contain one or more carbonyl l i g a n d s , and only these are considered here. 33 - At t h i s point a c l e a r d i s t i n c t i o n must be made between the nitrosyl halides and various nitrosonium s a l t s . i n v a r i a b l y form c a t i o n i c n i t r o s y l Cp M(C0) + m n NOV The l a t t e r reagents complexes, as shown i n eq. 13, [Cp M(C0) _ (N0)]V + CO m n 1 13. (m = 0 or 1 and n = 2-6 depending on M) since anions, A " , such as PFg" and BF^~ show a remarkable propensity to remain uncoordinated. Only one mole equivalent of carbon monoxide i s displaced and the product formed i s a 1:1 e l e c t r o l y t e . Any remaining coordinated carbonyl ligands are u s u a l l y quite s u s c e p t i b l e to displacement by even weakly n u c l e o p h i l i c neutral or anionic molecules such as acetone or halide anions (59, 60). The weakened metal-carbon bond in c a t i o n i c carbonyl compounds i s c o n s i s t e n t with current bonding t h e o r i e s , and the r e s u l t a n t enhanced l a b i l i t y of the CO ligand can be advantageously e x p l o i t e d i n the synthesis of both c a t i o n i c and neutral carbonyl compounds. On the other hand, the n i t r o s y l halides almost always react with metal carbonyls to form products which contain a coordinated halide l i g a n d . However, two cases of c a t i o n i c products s i m i l a r to those obtained with the nitrosonium s a l t s have been reported (61, 72a). For i n s t a n c e , both ClNO and BrNO react with F e ( C 0 ) ( P P h ) 3 3 2 in a c e t o n i t r i l e to give [ F e ( C 0 ) ( N 0 ) ( P P h ) ] X ~ . + 2 3 2 By f a r the most common mode of reaction i s that depicted in - 34 - equation 14 CpM(CO) + XNO m 'n r x ^ C p M ( C 0 ) _ ( N 0 ) X + 2C0 m n 14. 2 (m = 1 or 2 and n = 2-6 depending on M) which involves the coordination of one mole of XNO f o r every two moles of CO d i s p l a c e d . Since NO i s a stronger Tr-acceptor than CO, i t e f f e c t i v e l y competes with CO in the extent of u-backbonding with the central m e t a l , thereby r e s u l t i n g i n a weaker metal-carbon bond. Any remaining carbonyl ligand in the i n i t i a l product i s now s u f f i c i e n t l y l a b i l e to be displaced even by a c h l o r i n e atom which i s already coordinated to a t r a n s i t i o n metal. The r e s u l t i s the formation of dimers, or polymers of indeterminate l e n g t h , which contain c h l o r i n e bridges. These general p r i n c i p l e s are exemplified i n the following syntheses. Re(C0) (L)Cl + C1N0 * - Re(C0) (N0)LCl 4 2 + 2 2C0 (L = C H N , C H N0, C HgS, Bu P, P h P 0 , 4 - p i c o l i n e or 5 5 5 5 4 3 3 M(C0) + 2C1N0 [M(N0) Cl ] 6 2 2 n (63) 3,4-1utidine) + 6C0 (64) (M = Mo or W) Mo(C0) (PPh ) 4 3 2 + 2BrN0—»-Mo(N0) Br (PPh ) 2 2 3 2 LM(C0) (N Ph) + C1N0—*-LM(N0)(N Ph)Cl + 2C0 2 2 2 (M = Mo or W; L = H B ( p z ) : 3 M = Mo; L = Cp) + 4C0 (65) (66) - 35 - RB(pz) M(C0) (N0) + C1N0 3 e»-RB(pz) M(N0) Cl + 2CO 2 3 (M = Mo; R = H or pz: (10) 2 M = W; R = H) HB(3,5-Me pz) Mo(C0) (N0) + C1N0 —*-HB(3,5-Me pz) Mo(N0) Cl 2 3 2 2 3 (10) 2 + 2C0 The l a s t two of these r e a c t i o n s have a counterpart i n the cyclopentadienyl d e r i v a t i v e s , CpM(C0) (N0) (M = C r , Mo or W), and the 2 reaction of C1N0 with these complexes has been developed i n t o a high y i e l d synthetic route to the CpM(N0) Cl compounds, as described i n 2 Chapter IV. In t h i s chapter the reactions of ClNO with F e ( C 0 ) , 5 F e ( C 0 ) ( N 0 ) , [ C p F e ( C 0 ) ] , Co(C0) (N0) and CpCo(C0) are d e s c r i b e d . 2 3.2 2 2 2 3 2 Experimental A l l experimental procedures described here were performed under the same general conditions d e t a i l e d in s e c t i o n 2 . 2 . Reactions of n i t r o s y l c h l o r i d e with neutral complexes of iron and c o b a l t . To a vigorously s t i r r e d s o l u t i o n of Fe(C0) g (7.5 m l , 58 mmol) in CHgCl2 (30 ml) was added at room temperature a CH C1 2 containing C1N0 (7.37 g , 112 mmol). r e a c t i o n mixture became v i o l e t - b l a c k . 2 (50 ml) solution Gas was r a p i d l y evolved and the The f i n a l mixture was taken to dryness and the residue was extracted into hexanes (150 m l ) . The e x t r a c t was cooled to -78°C thereby p r e c i p i t a t i n g a dark red-brown s o l i d which Table IV. Reactions of N i t r o s y l Chloride with some Neutral Complexes of Iron and Cobalt. T r a n s i t i o n metal compd. (mmol) Amt. of C1N0 (mmol) Solvent (ml) Temp. Fe(C0) (N0) (28.8) 40 Pentane(20) 25° 29 2 Products(yields) Fe(N0) Cl(31%) 3 I s o l a t i o n and Identification P r e c i p i t a t e d from pentane at - 7 8 ° ; infrared spectrum >^,70 2 [CpFe(C0) ] (1.4) 2 2 4.0 CH C1 (30) 2 2 25° CpFe(C0) Cl(51%) 2 Sublimation at 50-60° (5xl0" mm); J infrared spectrum^ Co(C0) (N0) (4) CH C1 (60) 29 3 2 2 -78° [Co(N0) Cl] 2 2 I d e n t i f i c a t i o n in s o l u t i o n by . . . 2,69,70 infrared spectroscopy r CpCo(C0) (10) 9 a CH C1 (50) 2 2 -78° [Co(N0) Cl] 2 2 Sublimation at 90-100° (5x10 ~ j . 2,69,70 infrared spectrum , elemental a n a l y s i s . a A CH^Cl2 s o l u t i o n of ClNO was added u n t i l the disappearance of the infrared absorptions due to the i n i t i a l reactant. rmi) - 37 - was c o l l e c t e d by suction f i l t r a t i o n . In t h i s manner 3.0 g (17 mmol, 29% y i e l d ) of F e ^ O ^ C l , i d e n t i f i e d by i n f r a r e d spectroscopy ( 2 ) , was isolated. Fe(N0).jCl i s unstable at 25°C r e a d i l y l i b e r a t i n g n i t r i c o x i d e , e s p e c i a l l y under vacuum, so that an acceptable elemental a n a l y s i s f o r t h i s compound could not be obtained. The reactions of ClNO with other neutral complexes of i r o n and cobalt were performed s i m i l a r l y and the experimental d e t a i l s are summarized in Table IV. 3.3 3.3a Results and Discussion Reaction of n i t r o s y l c h l o r i d e with pentacarbonyliron, Fe(CO)^ . When a dichloromethane s o l u t i o n of Fe(C0)g i s treated with n i t r o s y l c h l o r i d e vigorous gas evolution occurs and the r e a c t i o n mixture becomes v i o l e t - b l a c k . The only n i t r o s y l containing product, Fe(N0).jCl, i s subsequently i s o l a t e d i n 29% y i e l d and i d e n t i f i e d by i t s c h a r a c t e r i s t i c i n f r a r e d spectrum (69, 70). Optimum y i e l d s are obtained when the r a t i o of n i t r o s y l c h l o r i d e to Fe(C0)g i s 2 : 1 , and r a t i o s l a r g e r than t h i s r e s u l t in a r a p i d l y diminishing y i e l d of F e ^ O ^ C l . In view of the high o x i d i z i n g property of n i t r o s y l c h l o r i d e , FeCl^ i s l i k e l y a byproduct of t h i s r e a c t i o n , although t h i s compound was not i s o l a t e d and i d e n t i f i e d . No i n f r a r e d spectral evidence was obtained f o r the p o s s i b l e formation of F e ( C 0 ) ( N 0 ) 2 a s 2 a n intermediate. However, treatment of F e ( C 0 ) ( N 0 ) 2 2 with n i t r o s y l c h l o r i d e under s i m i l a r experimental conditions did produce F e ^ O ^ C l in comparable y i e l d . u t i l i z i n g Fe(C0) i s much more convenient than the previously reported procedure (71). 5 This preparative route to Fe^O^d - 38 - Fe(N0) Cl i s a dark red-brown s o l i d which i s soluble in 3 common organic solvents i n c l u d i n g hexanes. The complex loses n i t r i c oxide at room temperature even under n i t r o g e n . Sublimation under vacuum i s p o s s i b l e but only with extensive attendant decomposition. This s u b s t a n t i a l thermal i n s t a b i l i t y thwarts a l l attempts to obtain an acceptable elemental a n a l y s i s for t h i s compound. Previous i n v e s t i g a t i o n s of the reactions of ClNO with Fe(C0) demonstrate that d i f f e r e n t reaction c o n d i t i o n s . 5 products may be obtained depending on In l i q u i d hydrogen c h l o r i d e the i s o l a b l e product i s [ F e ( C 0 ) ( N 0 ) ] C l ~ which r a p i d l y d i s s o c i a t e s to C1N0 and Fe(C0) at + 5 5 room temperature (72a). The s u r p r i s i n g l y low N-0 s t r e t c h i n g frequency of 1610 cm ^ displayed by t h i s compound i s i n d i c a t i v e of a n i t r o s y l ligand coordinated as NO", ije. a bent M-N-0 geometry. d i f f e r e n c e in the m e t a l - n i t r o s y l ClNO with Fe(C0) 5 Apart from the bonding modes, the e q u i l i b r i u m behaviour of bears resemblance to the coordination reaction of ClNO with a v a r i e t y of metal h a l i d e s , as exemplified by eq. 15 (15). C1N0 + F e C l , 3 ClN0-FeC1 -^-^N0 3 + + FeCl " 15. 4 In c o n t r a s t , other workers have found that n i t r o s y l c h l o r i d e and Fe(C0)g, i n a r a t i o of 1 . 5 : 1 , react at room temperature in a s t e e l bomb to give a mixture of F e ( C 0 ) ( N 0 ) and Fe(C0) 2 2 5 (72b). As the r a t i o i n c r e a s e s , lower y i e l d s of F e ( C 0 ) ( N 0 ) are obtained u n t i l , at the r a t i o of 2 . 7 : 1 , 2 2 only a mixture of carbon monoxide and oxides of nitrogen i s found. Unfortunately, the r e a c t i o n residue has not been examined for the p o s s i b l e - 39 - presence of F e ( N 0 ) C l . If the r e a c t i o n i s repeated in pentane under 3 ambient temperature and pressure, only a mixture of F e ( C 0 ) ( N 0 ) and 2 2 Fe(C0)g i s obtained. 3.3b Reaction of n i t r o s y l dienyl)iron], c h l o r i d e with b i s [ d i c a r b o n y l ( n - c y c l o p e n t a 5 [CpFe(C0) ] . 2 2 N i t r o s y l c h l o r i d e reacts with dimeric metal carbonyl complexes to produce monomeric, dimeric or polymeric n i t r o s y l compounds as shown i n eq. 16-18 (3, 63, 73). [CpRu(C0) ] 2 + C1N0 [Re(C0) Cl] 2 + Cl NO 2 4 [M(C0) C1 ] 4 2 *— CpRu(N0)Cl [Re(C0) (N0)Cl ] 2 + C1N0 2 16. 2 *-[M(N0)Cl ] 3 n 2 17. 2 + [M(N0) C1 ] 2 2 2 18. (M = Mo or W) In contrast to the r e a c t i o n depicted in eq. 16 we f i n d that [CpFe(C0) ] 2 compound. 2 i s cleaved by C1N0 without the formation of a n i t r o s y l The r e s u l t a n t CpFe(C0) Cl complex may be formed according to 2 the p l a u s i b l e r e a c t i o n scheme [CpFe(C0) ] 2 2 + C1N0 *»CpFe(C0) C1 + [CpFe(C0) ]~ + N0 2 2 followed by [ C p F e ( C 0 ) ] " + N0 2 + ^ [ C p F e ( C 0 ) ] + NO 2 2 + - 40 - with the second step being i d e n t i c a l to the oxidation of [CpFe(C0) ] 2 by ClNO as described in Chapter II. known a i r o x i d a t i o n of [ C p F e ( C 0 ) l 2 This transformation p a r a l l e l s the i n the presence of HC1 (68), 2 for which the f o l l o w i n g r e a c t i o n sequence may be surmised. [CpFe(C0) ] 2 2 + HC1 «*~CpFe(C0) Cl + CpFe(C0) H 2 2CpFe(C0) H 2 [CpFe(C0) ] + H 0 2 2 2 2 The hydrido complex i s known to undergo a i r o x i d a t i o n to give the i n i t i a l reactant dimer. In a s i m i l a r manner, the M ( C 0 ) - J Q (M = Mn 2 or Re) compounds are cleaved by C1N0 to a f f o r d only the M(C0) Cl species g (74). The formation of the metal halide complexes reported here does not comprise a useful synthetic method since better y i e l d s are more conveniently obtained according to e x i s t i n g procedures (68, 75). 3.3c Reactions of n i t r o s y l c h l o r i d e with tricarbonylnitrosylcobalt, Co(C0) (N0), and d i c a r b o n y l ( n - c y c l o p e n t a d i e n y l ) c o b a l t , 5 3 Both Co(C0) (N0) and CpCo(C0) react with n i t r o s y l 3 give [ C o ( N 0 ) C l ] 2 2 2 in moderate y i e l d s . CpCo(C0) . 2 c h l o r i d e to The r e a c t i o n i s rapid even at -78°C and the use of excess n i t r o s y l c h l o r i d e r e s u l t s in extensive decomposition. The dimeric [ C o ( N 0 ) C l ] 2 2 was p r e v i o u s l y prepared in a manner s i m i l a r to the preparation of Fe(N0) Cl (76). 3 of o l e f i n i c ligands by n i t r o s y l The displacement c h l o r i d e i s not unknown ( 3 ) , but the displacement of the cyclopentadienyl ligand has not been p r e v i o u s l y - 41 - reported. Thus, the formation of [ C o ( N 0 ) C l ] 2 i s unprecedented. 2 from CpCo(C0) and ClNO S i m i l a r l y , the n -cyclopentadienyl 5 2 ligand in CpRe(C0) has been shown to undergo a s i m i l a r displacement to y i e l d 3 the [ R e ( C 0 ) ( N 0 ) C l ] 2 reported (63). 2 2 dimer (74), which has been previously - 42 - CHAPTER IV CYCLOPENTADIENYLNITROSYL COMPLEXES OF CHROMIUM, MOLYBDENUM, AND TUNGSTEN 4.1 Introduction The number of c y c l o p e n t a d i e n y l n i t r o s y l complexes of the group VI t r a n s i t i o n metals has grown s t e a d i l y i n the past two decades. Both mono- and d i n u c l e a r species are known, and most d i s p l a y a r i c h and varied chemistry. The CpMtCO^NO) (M = Mo or W) compounds have been obtained in very low y i e l d s by the treatment of aqueous s o l u t i o n s of NaCCpMCCO)^] with n i t r i c oxide (77). Since these n u c l e o p h i l i c anions react with p r o t i c solvents to form the hydrido complexes, C p M ^ O ^ H , the synthesis l i k e l y occurs by attack of n i t r i c oxide on these hydrido intermediates. The cleavage of the weak metal-metal bond of [ C p C r ( C O ) . ^ with n i t r i c oxide affords the chromium c a r b o n y l n i t r o s y l analog i n good y i e l d s (78). However, since the dimeric precursor can be obtained only in low y i e l d s and with much expenditure of e f f o r t (79), t h i s route i s not p r a c t i c a l . synthetic Although a number of polynuclear carbonyl complexes react with n i t r i c oxide to produce mononuclear n i t r o s y l d e r i v a t i v e s , the metal-metal bonds i n [ C p M t C O ) ^ (M = Mo or W) are too strong to be cleaved by n i t r i c oxide. A more general n i t r o s y l a t i n g agent - 43 - i s D i a z a l d , which converts CpM(C0) H (M = Mo or W) to CpM(C0) (N0) in 3 reasonable y i e l d s (27, 80). 2 However, i t was r e c e n t l y found that the hydrido precursors are not necessary and the synthesis can be performed d i r e c t l y with the anions [CpM(C0) ]" (M = C r , Mo or W) (81) 3 e l i m i n a t i n g an unnecessary s y n t h e t i c procedure. thereby A number of substituted complexes CpM(CO)(N0)L containing a v a r i e t y of donar ligands has been reported (28). Another s e r i e s of r e l a t e d compounds can be represented by the general formula CpM(N0) Cl, of which the chromium d e r i v a t i v e i s the 2 most s t u d i e d . CrCl 3 It may be obtained in modest y i e l d when a mixture of and NaCgH i s treated with n i t r i c oxide (27, 29, 82). The 5 corresponding molybdenum compound i s obtained in poor y i e l d s by the reaction of T1C H with [Mo(N0) Cl ] 5 5 2 2 (83), or by the r e a c t i o n of NaN0 with [CpMo(C0) NH ]Cl in h y d r o c h l o r i c ' a c i d (84). 3 3 The p r e v i o u s l y unknown 3 tungsten analog, obtained by the treatment of [CpW(N0) (C0)]PFg with 2 NaCl (59), was reported s h o r t l y a f t e r our synthesis of t h i s complex. A number of compounds derived from C p C r ( N 0 ) C l , such as CpCr(N0) X 2 (X - F, Br, I, 2 CN, NCS, N0 and NCSe) (82, 8 5 ) , [CpCr(N0) L]C1, 2 2 [CpCr(N0)L ]Cl and CpCr(N0)(L)C1 (86) has already been obtained. 2 However, no d e r i v a t i v e s of the molybdenum and tungsten chloro complexes were known when t h i s research was undertaken. P r i o r to t h i s work, f i v e dinuclear chromium s p e c i e s , [CpCr(N0)L] 2 (L = NMe , SPh [CpCr(N0) ] 2 (90) had been c h a r a c t e r i z e d , and a l l these complexes 2 2 and SMe) (87, 88), C p C r ( N 0 ) N H contain bridging NO and/or L ligands (91-94). 2 2 3 2 (89), and The molybdenum dimers, - 44 - [CpMo(N0)L] (L = I, 2 SPh and SCH Ph), [CpMo(NO)L J (L = I, 2 2 2 SPh, SCH Ph 2 and C 0 R ) and [CpMo(NO)(SCH Ph)I] have a l l been derived from 2 f 2 [CpMo(N0)I ] 2 [CpMo(N0)I ] 2 2 2 2 rather than from CpMo(N0) Cl (95-97). The treatment of 2 with P P h , P(0Ph ) and CgHgN y i e l d s CpMo(N0)(L)I 3 3 2 (96). U n t i l now, the only known a l k y l and a r y l compounds of the type CpM(N0) R were the Me, E t , Ph and a - C H 2 (27, 98). 5 5 d e r i v a t i v e s of chromium The f i r s t three are obtained i n 60, 5, and 0.5 % y i e l d s , r e s p e c t i v e l y , by the r e a c t i o n of the corresponding Grignard reagent with e i t h e r CpCr(N0) Br or CpCr(N0) I. 2 In g e n e r a l , the c h l o r o n i t r o s y l 2 complex gives the poorest y i e l d s , and when THF i s s u b s t i t u t e d f o r E t 0 2 as s o l v e n t , the CpCr(N0) Me complex i s obtained i n only 1% y i e l d . 2 Interestingly, diazomethane i n s e r t s i n t o the Cr-Cl bond of CpCr(N0) Cl 2 to a f f o r d CpCr(N0) CH Cl i n 3% y i e l d , a r e a c t i o n s i m i l a r to the 2 2 i n s e r t i o n i n t o CpM(C0) H (M = Mo or W) and CpW(C0) CH to give the 3 3 3 corresponding methyl and ethyl d e r i v a t i v e s (27, 9 9 ) . The ^-CgHg d e r i v a t i v e i s obtained by the r e a c t i o n of NaC^Hg or TlC^Hg with the h a l o n i t r o s y l compound (18, 98). Recently, an i n t e r e s t i n g s e r i e s of complexes (C^Hg) Mo(N0)X 2 (X = I, Me and a-C^H^) has [CpMo(N0)I ] 2 2 been prepared. Thus, the treatment of with 2T1C H and 4T1C H y i e l d s (C H ) Mo(N0)I (83) and 5 5 5 5 5 5 2 (C H ) Mo(N0) (0-CgHj.) (100), and the r e a c t i o n of the former product with 5 5 2 MeMgBr produces ( C g H ^ M o (NO)Me (83). At room temperature, the NMR spectrum of each of the three (C(-H ) Mo(N0)X complexes e x h i b i t s only one 5 2 sharp cyclopentadienyl proton resonance. "18-electron r u l e " , an instantaneous In order to s a t i s f y the s t r u c t u r e containing r a p i d l y - 45 - interchanging n - and n - C H 5 3 g g rings was proposed (83). However, the x-ray s t r u c t u r e s of ( C H ) M o ( N 0 ) ( n ^ H g ) (101) and (C H ) Mo(N0)Me (102) 5 5 2 5 5 2 show that the n o n - n ' - C ^ r i n g s , though magnetically non-equivalent, are equivalent with respect to the c e n t r a l metal atom. Assuming s i m i l a r structures i n s o l u t i o n , the NMR behavior over a wide temperature range then does not require the n - C H =^==n -C H 5 fluxionality. 3 5 5 5 5 Moreover, the complexes (C H ) Mo(N0)S CNMe and [ P P h ] [(C^H ) Mo(N0)S CC(CN) ], 5 5 2 2 2 4 which have the c h e l a t i n g S CNMe and S C ( C N ) 2 2 2 2 2 2 2 l i g a n d s , contain both 2 n^-CgHg and n - C H g rings which become equivalent at 70°C due to 5 g rapid r ^ - C ^ : ^ ^ n - C H interchange 5 5 5 (103). This chapter describes the chain of events which subsequently leads to the a c q u i s i t i o n of the CpM(N0) R complexes, where M = C r , Mo 2 or W; R = a l k y l or a r y l . The s y n t h e t i c r o u t e , which i s g e n e r a l l y a p p l i c a b l e to a l l three m e t a l s , begins with the commercially a v a i l a b l e metal hexacarbonyl compounds, as in the scheme: M(C0) — N a [ C p M ( C 0 ) ] 6 ^-CpM(C0) (N0) 3 2 »-CpM(N0) Cl—*-CpM(N0) R 2 2 The success of t h i s preparative method i s l a r g e l y due to the high y i e l d synthesis of each intermediate compound, as described h e r e i n . Although the CpM(C0) (N0) species have been p r e v i o u s l y c h a r a c t e r i z e d , the 2 CpM(N0) Cl and CpM(N0) R compounds have not been thoroughly 2 studied 2 e i t h e r because of the d i f f i c u l t y i n t h e i r preparation or simply because they were p r e v i o u s l y unknown. of CpMo(C0) (N0), CpM(N0) X 2 2 Therefore, not only are the syntheses and CpM(N0) R d e s c r i b e d , but the chemical and 2 physical properties of some f u r t h e r d e r i v a r i v e s of CpM(N0) X are reported. 9 - 46 - 4.2 Experimental A l l experimental procedures described here were performed under the same general conditions d e t a i l e d in section 2 . 2 . 4.2a Preparation of d i c a r b o n y l ( n - c y c 1 o p e n t a d i e n y l ) n i t r o s y l complexes 5 of chromium, molybdenum and tungsten, CpM(C0) (N0) (M = C r , Mo or W). 2 The success of the high y i e l d syntheses of the C p M ^ O ^ N O ) complexes depends on the a v a i l a b i l i t y of the Na[CpM(C0) ] anions 3 uncontaminated by any NaC^Hg. The molybdenum and tungsten s a l t s were obtained according to a published procedure (27), although a 5% mole excess of the M(C0)g compounds was used to improve the y i e l d s of the desired anions. A l s o , the tungsten r e a c t i o n was allowed to continue f o r 70 h i n order to ensure more complete conversion. The chromium s a l t was e f f i c i e n t l y prepared in the f o l l o w i n g manner. A THF s o l u t i o n containing NaCgHg (27) (4.18 g , 47.5 mmol) was concentrated in vacuo j u s t u n t i l a s l u r r y formed (approx. 20 m l ) . n-Butyl ether (100 m l ; Eastman Kodak p r a c t i c a l grade) and Cr(C0)g (11.0 g, 50.0 mmol; Pressure Chemical Co.) were added and the mixture was heated under gentle r e f l u x 12 h with vigorous s t i r r i n g . room temperature and f i l t e r e d . for The f i n a l mixture was allowed to cool to The pale yellow s o l i d thus c o l l e c t e d was washed with n-butyl ether (3 x 30 ml) and once with hexanes (30 m l ) , and dried at 25°C (5 x 1 0 " mm) f o r 18 h. 3 The Na[CpM(C0) ] complexes 3 of molybdenum and tungsten were freed of any unreacted M(C0)g by simply taking the f i n a l r e a c t i o n mixture to dryness in vacuo and heating - 47 - the residue to 60° (5 x 10" mm) f o r 12 h. without f u r t h e r A l l three s a l t s were used purification. The three CpM(C0) (N0) complexes were prepared s i m i l a r l y and 2 the experimental procedure using the molybdenum complex as a t y p i c a l example, was as f o l l o w s . To a r a p i d l y s t i r r e d THF s o l u t i o n (120 ml) NaCCpMo^O^] containing (13.0 g , 48.7 mmol) was added dropwise at room temperature a s o l u t i o n of Diazald (10.4 g , 48.6 mmol; Eastman Kodak reagent grade) i n THF (50 m l ) . Gas was evolved and an orange s o l i d p r e c i p i t a t e d . The f i n a l r e a c t i o n mixture was taken to dryness in vacuo and sublimation of the residue at 60°C (5 x 10 mm) onto a water-cooled probe for 18 h produced 11.2 g (45.3 mmol, 93% y i e l d ) of pure CpMo(C0) (N0). analytically The chromium and tungsten compounds were obtained 2 i n y i e l d s of 82 and 84% r e s p e c t i v e l y . A n a l . Calcd. f o r C H C r ( C 0 ) ( N 0 ) : 5 Found: 1945(s).- 5 2 C, 41.40; H, 2.60; N, 6.70. v(C0) cm" v(N0) cm" 1 (in C H C 1 ) : 2 5 1937(s). 5 2 C, 34.28; H, 2.24; N, 5.54. v(N0) cm" 1 (in CHpClpj: C, 25.29; H, 1.70; N, 4 . 1 3 . v(N0) cm" 1 (in-CH^C"^): 1 (in C H C 1 ) : 2 2 2020(s); 1663(s). 2 1925(s). 2020(s); C, 34.03; H, 2.04; N, 5.67. v(C0) cm" Calcd. f o r C,-HgW(C0) (NO): Found: (in CHpClp): 1 1680(s). 2 C a l c d . f o r C H Mo(C0) (N0): Found: C, 41.39; H, 2.48; N, 6.90. C, 25.10; H, 1.50; N, 4.18. v(C0) c m 1655(s). -1 (in C H C 1 ) : 2 2 2010(s); - 48 - 4.2b Preparation of chloro(n -c,yclopentadienyl )dinitrosy1 complexes of 5 chromium, molybdenum All manner. and tungsten, CpM(N0) Cl (M = C r , Mo or W) . 2 three CpM(N0) Cl compounds were prepared i n a s i m i l a r 2 The y i e l d s of the chromium and tungsten complexes were optimized by performing the reactions at -78°C. The molybdenum compound was obtained in e x c e l l e n t y i e l d s even at room temperature and a t y p i c a l synthesis was as f o l l o w s . A CH C1 2 2 s o l u t i o n (100 ml) containing CpMo(C0) (N0) (6.5 g , 2 26 mmol) was treated dropwise with r a p i d s t i r r i n g at room temperature with a s o l u t i o n of ClNO i n C H C 1 . 2 2 Gas e v o l u t i o n occurred and the i n i t i a l orange s o l u t i o n became dark green. The course of the r e a c t i o n was followed by i n f r a r e d spectroscopy and C1N0 was added j u s t u n t i l the carbonyl absorptions due to the reactant disappeared. (Great care was taken not to add excessive amounts of ClNO since t h i s r e s u l t e d i n a s i g n i f i c a n t reduction i n the y i e l d of the desired product. Conversely i f i n s u f f i c i e n t C1N0 was employed, then some d i f f i c u l t y was encountered i n the separation of the unreacted CpM(C0) (N0) from 2 the desired product.) The f i n a l r e a c t i o n mixture was concentrated in vacuo to ca. 30 ml and f i l t e r e d through a short ( 3 x 5 cm) F l o r i s i 1 column. The column was washed with CH C1 2 2 u n t i l the washings were c o l o r l e s s , and the combined f i l t r a t e s were taken to dryness to give 6.0 g (2.3 mmol, 90% y i e l d ) of a n a l y t i c a l l y pure CpMo(N0) Cl. 2 The chromium and tungsten complexes were obtained i n y i e l d s of 77 and 72% respectively. Table V. Elemental Analyses and Physical Properties of CpM(N0) X (M = C r , Mo or W; X = Cl or 9 Color Compound Mp, °C (under N ) Analyses, % Proton NMR, x(in C D ) 2 CpCr(N0) Cl 9 CpMo(N0) Cl 2 CpW(N0) Cl 2 CpCr(N0) I 2 CpMo(N0) I 2 CpW(N0) I 9 gold green green dark gold o l i v e green o l i v e green 144 (dec) 116 127 (dec) 146 (dec) 114 (dec) 129 (dec) I). g 6 v(N0) c m ( i n CH C1 ) -1 2 2 H N Cl ^ " 5 5 5.22(s) 1816(s), 1711(s) 4.93(s) 1759(s), 1665(s) 5.02(s) 1733(s), 1650(s) 5.28(s) 1808(s), 1718(s) 5.00(s) 1764(s), 1677(s) 4.94(s) 1740(s), 1657(s) calcd: 28.26 2.37 13.18 16.68 found: 28.29 2.55 12.86 16.99 calcd: 23.42 1.96 10.92 found: 23.53 1.90 10.70 calcd: 17.44 1.46 8.13 10.29 found: 17.68 1.62 8.10 10.26 calcd: 19.75 1.66 9.22 found: 19.71 1.76 9.00 calcd: 17.26 1.45 8.05 found: 17.33 1.40 7.88 calcd: 13.78 1.16 6.43 found: 13.78 1.17 6.36 5 C H - 50 - The complexes, along with t h e i r elemental analyses and physical p r o p e r t i e s , are l i s t e d in Table V. 4.2c Preparation of ( n - c y c l o p e n t a d i e n y l ) i o d o d i n i t r o s y l 5 chromium, molybdenum complexes of and tungsten, CpM(N0),,I (M = C r , Mo or W). A l l the CpM(N0) I complexes were prepared i n a s i m i l a r manner 2 and the customary procedure f o r the synthesis of the CpCr(N0) I 2 compound was as f o l l o w s . A THF s o l u t i o n (150 ml) containing CpCr(N0) Cl (2.54g, 12.0 2 mmol) and Nal (9.0 g , 60 mmol; M a l l i n c k r o d t reagent grade) was s t i r r e d at room temperature f o r 18 h. The r e a c t i o n mixture became a very dark yellow-brown in c o l o r and a white s o l i d formed. The f i n a l mixture was taken to dryness in vacuo and the r e s u l t a n t residue extracted i n t o CH C1 2 2 (150 ml). The e x t r a c t was f i l t e r e d through a short ( 3 x 5 cm) F l o r i s i 1 column and taken to dryness i n vacuo (5 x 10 mm) thereby a f f o r d i n g a v i r t u a l l y q u a n t i t a t i v e y i e l d of the a n a l y t i c a l l y pure CpCr(N0) I complex. 2 The elemental analyses and physical properties of a l l three CpM(N0) I compounds are given i n Table V. 2 4.2d Preparation of b i s [ ( n - c y c l o p e n t a d i e n y 1 ) e t h o x o n i t r o s y l c h r o m i u m ] , 5 [CpCr(N0)(0Et)] . 2 A s o l u t i o n of CpCr(N0) Cl (2.13 g , 10.0 mmol) in EtOH (120 ml) 2 was treated with NaOEt (0.80 g , 12.0 mmol) at room temperature. Immediately, the mixture became y e l l o w - r e d and a f i n e white s o l i d formed. - 51 - The mixture was s t i r r e d f o r 0.5 h and the i n f r a r e d spectrum of the supernatant l i q u i d displayed absorptions at 1792 c m ( s ) and 1585 c m ( s ) -1 i n d i c a t i v e of the CpCr(N0) (0Et) complex (cf. i n f r a r e d spectrum of 2 C p C r ( N 0 ) C l , v(N0) cm" (in EtOH): 1812(s); 1708(s)). 1 2 removed i n vacuo y i e l d i n g a red o i l . (5 x 10 -1 The solvent was During f i n a l drying at 25°C mm) f o r 0.5 h, the red o i l was transformed to a green s o l i d . This product was extracted i n t o CH^Cl^ (25 ml) and chromatographed through a F l o r i s i 1 column (2.5 x 8 cm) with CH C1 2 eluate was taken to dryness in vacuo (5 x 10 2 as e l u e n t . mm) y i e l d i n g 0.64 g (3.3 mmol, 33% y i e l d ) of the o l i v e - g r e e n [CpCr(N0)(0Et)] A n a l . Calcd. f o r [C H Cr(N0)(0Et)] : 5 N, 7.40. 1660. Found: 5 compound. 2 C, 43.58; H, 5 . 2 1 ; 2 C, 43.78; H, 5.26; N, 7.29. Mp. (under N ) : The v(N0) cm" 1 (in C H C 1 ) : 2 2 233°C (dec). 2 The CpM(N0) Cl (M = M or W) complexes reacted with LiOEt i n 2 THF producing y e l l o w - r e d s o l u t i o n s which, when taken to dryness, y i e l d e d yellow-red o i l s . 95°C (5 x 10 These o i l s remained unchanged even a f t e r heating at mm) f o r 2 h. Their i n f r a r e d spectra suggested that the products were CpMo(N0) Et (v(N0) cm" (in C H C 1 ) : 1 2 and CpW(N0) Et (v(N0) cm" 2 4.2e Preparation of 1 2 (in C H C 1 ) : 2 2 2 1740(s); 1630(s)) 1710(s); 1610(s)). bis[ch1oro(n -cyclopentadieny1)nitrosylchromium], 5 [CpCr(N0)Cl] , 2 A sample of [CpCr(N0) (0Et)] (0.19 g , 1.0 mmol) was d i s s o l v e d i n 2 2 benzene (30 ml) and dry HCl(g) was bubbled through the s o l u t i o n . Immediately, the off-green reaction mixture became a very intense green - 52 - in color. Enough HCI(g) was added to j u s t completely consume the i n i t i a l reactant (monitored by i n f r a r e d spectroscopy). The mixture was taken to dryness in vacuo and the product c r y s t a l l i z e d from CH C1 2 (20 ml) by the a d d i t i o n of hexanes (50 m l ) . 2 The s o l i d was c o l l e c t e d by f i l t r a t i o n and d r i e d at 25°C (5 x 10~ mm) to give 0.16 g (0.88 mmol, 3 88% y i e l d ) of the green [CpCr(N0)C1] complex. g A n a l . Calcd. f o r [ C ^ C r (N0)C1 ] : 2 Found: C, 32.50; H, 2 . 6 1 ; N, 7.66. C, 32.90; H, 2.76; N, 7.67. v(N0) cm" 1 (in C H g C l ) : 2 1678. Mp. (under N ) : 140 (dec). 2 4.2f Preparation of a l k y l - and a r y l - ( n - c y c ! o p e n t a d i e n y l ) d i n i t r o s y l 5 complexes of chromium, molybdenum and tungsten, CpM(N0) R 2 (M = C r , Mo or W; R = a l k y l or a r y l ) . Since the various a l k y l and a r y l d e r i v a t i v e s were s i m i l a r l y prepared, two representative syntheses are described below. Table VI summarizes the p a r t i c u l a r experimental d e t a i l s . 4.2fl Preparation of ( n - c y c l o p e n t a d i e n y l ) m e t h y l d i n i t r o s y l t u n g s t e n , 5 CpW(N0) Me . 2 A benzene s o l u t i o n (12 ml) containing jte^Al (0.22 g , 3.1 mmol; Texas A l k y l s ) was added dropwise at room temperature to a s t i r r e d of CpW(N0) Cl (1.0 g , 2.9 mmol) in benzene (25 ml). 2 solution The green s o l u t i o n was allowed to s t i r f o r 48 h during which time a red-brown o i l y s o l i d deposited on the w a l l s of the r e a c t i o n f l a s k . (The r e a c t i o n was followed - 53 - Table VI. Reaction Conditions and P u r i f i c a t i o n Methods for CpM(N0) R . 9 Compound CpCr(N0) C H 2 g CpCr(N0) CH 2 2 2 4 g CpMo(N0) CH 2 2 CpW(N0) CH 2 3 5 (CH ) A1 0.5 AB (C H ) A1 0.5 A (i-C H ) A!H 0.5 A (C H ) A1 1 .5 AA (CH ) A1 1 A (C H ) A1 1 A g 0.5 A 1 AB 48 AB 3 3 5 3 4 g 5 2 3 3 2 5 4 g AB 3 CpMo(N0) i-C H 2 0.5 5 6 3 2 CpW(N0) C H g 5 CpMo(N0) C H 2 (C H ) A1 2 5 2 2 Purification methods 3 CpCr(N0) i-C H CpMo(N0) C H Reaction time (hours) 6 5 3 CpCr(N0) C H A l k y l a t i n g or A r y l a t i n g Agent 5 3 (i-C H ) A!H 4 W g 2 A1 3 (CH ) A1 3 3 + A - chromatographic separation on alumina using benzene as the e l u a n t . B - sublimation i n vacuum - 54 - by i n f r a r e d spectroscopy and such monitoring of several experiments showed these to be the optimum stoichiometry and reaction time.) Judging from the r e l a t i v e v(N0) band i n t e n s i t i e s of the f i n a l reaction mixture, the CpW(N0) Me product and unreacted CpW(N0) Cl e r e present 2 2 in ca_. equimolar q u a n t i t i e s . W The r e a c t i o n mixture was concentrated in vacuo to c a . 15 ml and the supernatant l i q u i d chromatographed i n a short ( 3 x 7 as eluent. cm) column of alumina (Woelm neutral grade 1) with benzene The eluate was taken to dryness in vacuo and the r e s u l t a n t _q s o l i d sublimed at 30°C (5 x 10 mm) onto a water-cooled probe a f f o r d i n g 0.20 g (0.62 mmol, 20% y i e l d ) of a n a l y t i c a l l y pure CpW(N0) Me. 2 4.2f2 Preparation of [n -cyclopentadieny1)dinitrosylphenylmo1ybdenum, 5 CpMo(N0) Ph . 2 A s o l u t i o n of Ph Al (28) (0.35 g , 1.4 mmol) i n benzene (70 ml) 3 was added dropwise to a s o l u t i o n of CpMo(N0) Cl (1.0 g , 3.9 mmol) i n the 2 same solvent (30 ml). A red-brown s o l i d formed and the mixture was f u r t h e r s t i r r e d for 1 h at which point the i n f r a r e d spectrum of the supernatant l i q u i d confirmed the depletion of the i n i t i a l reactant. The f i n a l reaction mixture was concentrated i n vacuo to c a . 20 ml and the supernatant l i q u i d was chromatographed on an alumina column. The product was eluted with benzene and only the main portion of the green product band was c o l l e c t e d . The solvent was removed from the eluate and the residue was d r i e d at room temperature i n vacuo (5 x 10 mm) f o r 4 h thus providing 0.65 g (2.2 mmol, 56% y i e l d ) of CpMo(N0) Ph as an 2 a n a l y t i c a l l y pure o l i v e - g r e e n o i l . - 55 - A l l the other complexes i n Table VII were obtained in y i e l d s of 30-50%. Their elemental analyses and physical properties are given in Tables VII and V I I I . A l l the complexes are stable in a i r f o r short periods of time but are best stored under nitrogen and below 0°C. They are very soluble i n common organic solvents i n c l u d i n g hexanes. 4.2g Preparation of bis[(n -cyclopentadienyl)dinitrosylchromium], 5 [CpO(N0) ] . 2 2 To an amalgam made from sodium (0.5 g , 20 mmol) and mercury metal (20 ml) was added a s o l u t i o n of CpCr(N0) Cl (1.06 g , 5.00 mmol) i n 2 benzene (120 ml). This reaction mixture was s t i r r e d vigorously at room temperature u n t i l the i n f r a r e d spectrum of the supernatant liquid contained no absorption bands due to the i n i t i a l reactant (ca_. 1.5 h). [Reaction beyond t h i s point led to decomposition of the desired product.] During the course of the reaction a grey s o l i d was deposited and the s o l u t i o n became red-purple in c o l o r . The supernatant l i q u i d was syringed from the amalgam and concentrated in vacuo to ca_. 20 ml. This s o l u t i o n was t r a n s f e r r e d to a short (2 x 5 cm) column of alumina (Woelm neutral grade 1) and the column was eluted with benzene u n t i l the washings were c o l o r l e s s (ca_. 120 m l ) . Solvent was removed from the eluate in vacuo and the remaining purple-black s o l i d was dried at room temperature under high vacuum'(5 x 10 mm) f o r 2 h. In t h i s manner 0.68 g (1.9 mmol, 77% y i e l d ) of the a n a l y t i c a l l y pure [ C p C r ( N 0 ) l 2 2 complex was obtained. Anal. Calcd. for [ ( C H ) C r ( N 0 ) ] : 5 Found: 1512(m). 5 C, 33.78; H, 2.75; N, 15.82. Mp. (in a i r ) : 147°C (dec). 2 2 C, 33.91; H, 2.85; N, 15.82. v(N0) c m -1 (in C H C 1 ) : 2 2 1667(s); - 56 - Table VII. Elemental Analyses and Physical Properties of CpM(N0) R. 9 Compound Color Mp,°C ( CpCr(N0) C H 2 g CpCr(N0) CH 2 3 CpCr(N0) C H 2 5 2 5 CpCr(N0) i-C H 2 4 CpMo(N0) C H 2 6 CpMo(N0) CH 2 5 2 5 CpMo(N0) i-C H 2 4 CpW(N0) CgH 2 CpW(N0) CH 2 3 5 g a i r Analyses,% ) C calculated H N C found H dark green 48-48.5 51.97 3 .97 11 .02 52 .05 4 .10 10 .97 dark green 80.5-81.0 37.51 4 .20 14 .58 37 .42 4,.19 14 .49 green oil 40.79 4 .89 13 .59 40 .74 4,.90 13 .46 green oil 46.15 6 .03 11 .96 46 .38 6,.20 11 .62 o l i v e green oil 44.31 3 .38 green 3 CpMo(N0) C H 2 g i n 61.5-62.0 green oil green oil 9 .40 44 .28 3,.46 9 .13 30.53 3 .42 11 .87 30 .69 3 .33 11 .82 33.52 4 .03 11 .20 34 .05 4 .38 10 .90 . 38.86 5 .07 10 .07 39 .33 5 .23 10 .06 green 109-110 34.22 2 .61 7 .26 34 .38 2 .74 7 .03 pale green 75-76 22.24 2 .49 8 .65 22 .54 2 .42 8 .60 - 57 - Table VIII. IR and 'h! NMR Data f o r CpM(N0) R. 2 Compound IR a v(N0) cm" CpCr(N0) Cl 2 CpCr(N0) C H 2 6 CpCr(N0) CH 2 3 CpCr(N0) C H 2 5 2 5 CpCr(N0) i-C H 2 4 g CpMo(N0) Cl 2 CpMo(N0) C H 2 g CpMo(N0) CH 2 3 CpMo(N0) C H 2 5 2 5 CpMo(N0) i-C H 2 4 CpW(N0) Cl 2 CpW(N0) C H 2 g CpW(N0) CH 2 3 5 g ] n -C,-rL 1 5 H NMR x ( i n CgDg) others 5.22 - 1690 5.27 2.7(m) 1780 1675 5.63 9.55 ( s i n g l e t CH ) 1772 1670 5.45 8.6(m) 1775 1675 5.33 8-9(m) 1758 1665 1745 1658 . 4.90 2.7(m) 1728 1640 4.92 9.20 ( s i n g l e t CH ) 1735 1643 4.90 8.2(m) 1725 1638 4.93 7.6-8.8(m) 1733 1650 5.02 - 1713 1630 4.95 2.6(m) 1705 1620 4.98 8.82 ( s i n g l e t CH ) 1815(s) 1710(vs) 1792 b b b 3 - 4.93 3 3 Hexane s o l u t i o n unless indicated otherwise. Dichloromethane s o l u t i o n . Approximate centroid of complex m u l t i p l e t C (m). - 58 - 4.3 4.3a Results and Discussion The d i c a r b o n y l ( n - c y c l o p e n t a d i e n y l ) n i t r o s y l 5 complexes of chromium, molybdenum and tungsten, CpM(C0)p(N0) (M = C r , Mo or W) . A l l three CpM(C0) (N0) compounds were obtained according to the 2 f o l l o w i n g sequence of r e a c t i o n s : NaC H + M(C0) 5 5 * - Na[CpM(C0) ] + 3C0 6 3 Na[CpM(C0) ] + p-CH C H S0 N(N0)CH 3 3 6 4 2 ——»~ 3 CpM(C0) (N0) + C0 + p-CH C H S0 N(CH )Na 2 3 6 4 2 3 The success of t h i s synthetic route depends c r i t i c a l l y on the a v a i l a b i l i t y of the corresponding Na[CpM(C0) ] s a l t s which are free of any unreacted 3 NaCgHg. The presence of t h i s contaminant i s immediately evident upon subsequent reaction with Diazald since a brown-black, rather than the expected orange-red, reaction mixture i s obtained. Furthermore, the y i e l d of the desired c a r b o n y l n i t r o s y l i s d r a s t i c a l l y reduced. However, once the s u f f i c i e n t l y pure anions are obtained, t h e i r r e a c t i o n with Diazald in THF produces the CpM(C0) (N0) complexes i n e x c e l l e n t , 2 reproducible y i e l d s ranging from 82-93%, depending on M. A l s o , these syntheses can be e a s i l y scaled to produce the desired products in q u a n t i t i e s as large as 30 g while s t i l l maintaining the same high y i e l d s . Undoubtedly, the experimental procedures described f o r the preparation of these complexes are the most convenient thus f a r developed (27, 77, 78, 80, 81 ). - 59 - The Na[CpM(C0) ] (M = Mo or W) s a l t s can be r e a d i l y o b t a i n e d , 3 i n THF under r e f l u x , according to a published procedure (27). However, to ensure complete conversion important modifications have been n e c e s s a r i l y made. Thus, the syntheses are performed with NaCp as the l i m i t i n g reagent and the r e a c t i o n i n v o l v i n g the tungsten compound i s allowed to continue f o r the extended period of 72 hours. Unfortunately, under the same c o n d i t i o n s , Cr(C0)g and NaC^Hg react very slowly and the conversion a f t e r seven days of reaction i s s t i l l r e l a t i v e l y low. Although diglyme has been previously employed in the preparation of Na[CpCr(C0) ] (79), 3 i t s strong s o l v a t i n g c h a r a c t e r i s t i c s renders i t s use i m p r a c t i c a l . However, i f Cr(C0)g and NaCgHg are allowed to react i n n-BupO under r e f l u x f o r 18 hours, a v i r t u a l l y q u a n t i t a t i v e y i e l d of the desired product i s obtained. The Na[CpCr(C0) ], i n s o l u b l e i n n-BupO, p r e c i p i t a t e s 3 as a c r y s t a l l i n e pale yellow s o l i d during the course of the r e a c t i o n . Subsequent p u r i f i c a t i o n , to remove excess M(C0)g, of the Na[CpM(C0) ] 3 compounds i s e a s i l y performed as described in the Experimental s e c t i o n . The properties of the C p M ^ O ^ N O ) compounds have been previously described (2, 3, 28). The complexes are orange to orange-red s o l i d s r e a d i l y soluble i n organic solvent and stable in a i r f o r periods of time. However, they may be stored i n d e f i n i t e l y short under nitrogen at room temperature. 4.3b The c h l o r o ( n - c y c 1 o p e n t a d i e n y l ) d i n i t r o s y l 5 complexes of chromium, molybdenum and tungsten, CpM(N0) Cl (M = C r , Mo or W). 9 The high y i e l d syntheses of a l l three complexes are e f f e c t e d by - 60 - the treatment of CpM(C0) (N0) with C1N0 in C H C 1 , according to eq. 19. 2 2 CpM(C0) (N0) + C1N0 2 e-CpM(N0) Cl + 2C0 2 2 19. (M = C r , Mo or W) In order to maximize y i e l d s , the transformations i n v o l v i n g the chromium and tungsten containing compounds must be performed at -78°C, while the molybdenum complex can be obtained i n e x c e l l e n t y i e l d s at room temperature. The l a t t e r r e a c t i o n i s accompanied by the formation of a small amount of [ C p M o ( N 0 ) C l ] , i d e n t i f i e d by elemental a n a l y s i s and i t s c h a r a c t e r i s t i c 2 2 i n f r a r e d spectrum (104). Since t h i s byproduct can a l s o be formed by the d i r e c t treatment of CpM(C0) (N0) with C l 2 2 (104), i t s appearance simply r e f l e c t s the f a c t that ClNO e x i s t s in s o l u t i o n as part of the equilibrium 2C1N0-^ — 2N0 + C l 2 As in most reactions between the n i t r o s y l halides and metal c a r b o n y l s , special a t t e n t i o n must be taken to avoid excess n i t r o s y l h a l i d e . T y p i c a l l y , the above conversions are followed by i n f r a r e d spectroscopy and enough C1N0 i s added u n t i l the carbonyl absorptions of the reactant have j u s t disappeared. In t h i s manner, the f u r t h e r r e a c t i o n of the desired products i s e f f e c t i v e l y prevented. In any case, the general a p p l i c a b i l i t y of the reaction given by eq. 19, u t i l i z i n g the now r e a d i l y a v a i l a b l e s t a r t i n g m a t e r i a l s , makes t h i s high y i e l d preparative route superior to a l l others thus f a r reported (27, 29, 59, 83, 84, 105). - 61 - The CpM(N0) Cl complexes, along with some of t h e i r physical 2 p r o p e r t i e s , are presented in Table V. They are c r y s t a l l i n e s o l i d s which have low s o l u b i l i t y in hexanes but are very soluble in most other organic s o l v e n t s . Contrary to a previous report (83), CpMo(N0) Cl, as 2 well as the chromium and tungsten d e r i v a t i v e s , are stable indefinitely under nitrogen at room temperature, and a l l three can be exposed to a i r f o r short periods of time without noticeable decomposition. Furthermore, the molybdenum complex melts at 116°C without decomposition and a l l three compounds may be sublimed at 40-50°C (5 x 10 mm) although some decomposition occurs with the chromium and tungsten s p e c i e s . Chemically, the CpM(N0) Cl compounds are useful 2 precursors f o r the synthesis of a wide v a r i e t y of stable a l k y l and a r y l complexes, CpM(N0) R, as discussed subsequently. 2 A l l three CpM(N0) I complexes are obtained in 2 y i e l d s by the d i s p r o p o r t i o n a t e quantitative r e a c t i o n between Nal and the corresponding chloro complexes i n THF. Their physical (Table V) and chemical properties are very s i m i l a r to those of the chloro compounds. The molybdenum and tungsten complexes have not been p r e v i o u s l y reported. The x-ray c r y s t a l structure of CpCr(N0) Cl i n d i c a t e s a pseudo2 tetrahedral ("piano s t o o l " ) arrangement of ligands about the chromium atom (106) as in C. The Cj-H^ r i n g randomly occupies one of two coplanar O - 62 - o r i e n t a t i o n s i n which a l l the Cr-C distances are approximately e q u a l , the o average distance being 2.20 A. The Cr-NObond distances of 1.717 (0.012) and 1.704 (0.013) A , which are v i r t u a l l y i d e n t i c a l to the value of 1.716 (0.003) found in CpCr(N0) (NC0) (107), are about 0.4 A shorter than the expected Cr-N(sp) 2 bond length. In f a c t , the Cr-N bond order i s estimated to be 1.7, i n d i c a t i n g the n i t r o s y l i s bonded as N0 with appreciable e l e c t r o n + donation from the Cr(d) to the N(pir*) o r b i t a l s . The Cr-N-0 fragments i n both the chloro and isocyanato compounds depart from l i n e a r i t y by about 10°. This i s ascribed to e l e c t r o s t a t i c r e p u l s i o n between the oxygen atom of the n i t r o s y l ligand and the c h l o r i d e or isocyanate l i g a n d rather than to c r y s t a l packing f o r c e s . The mass spectral data for the CpM(N0) Cl complexes, given i n 2 Tables IX and X, e x h i b i t the expected fragmentation p a t t e r n s . The presence of MCp and MCpCl and the concurrent absence of M(N0) and + + + M(N0)C1 fragments can be a t t r i b u t e d to the f a c t that the M-Cp linkage + i s stronger than the M-N0 bond. The mass spectrum of CpMo(C0) (N0) d i s p l a y s a s i m i l a r behavior (108). 2 Furthermore, as i s found in the cases of CpFe(C0) Cl (108) and CpMo(C0) Cl (109), the M-Cp and M-Cl bonds 2 3 in the CpM(N0),,Cl complexes are ruptured with about equal difficulty. The [ M C H ] fragments, which occur frequently i n the mass spectra of + 3 3 Cp-containing complexes, are not observed f o r the chromium compound but become i n c r e a s i n g l y abundant for the molybdenum and tungsten analogs. a d d i t i o n , the r e l a t i v e abundance of fragments containing the n i t r o s y l group suggest a M-N0 bond strength which increases as Mo < Cr < W, In - 63 - Table IX. High Resolution Mass Spectral Data f o r C p C r ( N 0 ) C l . 9 measured m/e ' calculated relative abundance assignment 213.9423 213.9414 11.9 C H Cr(N0) 211.9440 211.9444 32.6 C H Cr(N0) 183.9447 183.9434 13.8 C H Cr(N0) Cl + 181.9476 181.9464 36.6 C H Cr(N0) Cl + 153.9459 153.9455 36.6 151.9481 151.9484 100 176.9796 176.9756 5.3 C H Cr(N0) 146.9818 146.9776 3.4 C H Cr(N0) 116.9784 116.9796 18.0 C H Cr 88.9050 88.9063 10.6 Cr Cl + 86.9089 86.9093 23.9 Cr + 65.0396 65.0391 13.3 C 51.9412 51.9404 13.8 Cr 5 37 5 5 5 2 Cl" Cl 2 3 7 5 5 3 5 5 5 37 5 5 + 35 + C H C r °C1 5 5 5 5 c c 5 + 5 3 7 3 5 5 5 H + Cl + + + 2 - 64 - Table X. Low Resolution Mass Spectral Data f o r CpM(N0) Cl . a 2 (M = Mo or W) CpMo(N0) Cl CpW(N0) Cl 2 2 m/e m/e Relative Abundance Assignment 258 43.7 C H Mo(N0) Cl 228 33.5 C H Mo(N0)Cl 198 100 C H MoCl + 172 30.4 C H MoCl + 163 7.5 C H Mo + 137 12.4 C H Mo + 133 24.2 MoCl 98 10.4 Mo 65 3.7 a 5 c 9 8 Mo, 5 3 3 5 5 3 1 8 4 + + 344 100 C H W(N0) C1 314 81.0 C H W(N0)C1 284 53.7 C H WC1 258 71.4 C 249 28.1 CHW 223 13.0 C 219 16.0 WC1 184 2.1 w 65 6.8 C 5 5 5 + 2 + 5 0 5 C 2 c O The assignments i.e. 5 Assignment Relative Abundance 3 + + 5 5 H + 5 3 3 H 5 W C 1 + + 5 3 3 H W + + + 5 5 H + involve the most abundant n a t u r a l l y occurring W and 3 5 C 1 , in each fragment. + 5 isotopes, - 65 - s i m i l a r to the ordering of the M-CO bond strengths i n the CpM(C0) Cl 3 compounds (28). A wide v a r i e t y of d e r i v a t i v e s of the type CpCr(N0) X (X = F, Br, 2 I, CN, NCS, N0 (82), and NCSe (85)) have been obtained by the 2 treatment of an aqueous s o l u t i o n of [ C p C r ( N 0 ) ] , generated from CpCr(N0) Cl and + 2 AgNO-j, with NaX or KX. 2 The isoselenocyanato complex decomposes r e a d i l y i n s o l u t i o n to give CpCr(N0) CN and elemental selenium. Also, 2 CpCr(N0) SCF i s formed when the chloro compound i s allowed to react with 2 3 AgSCF i n acetone (110). 3 In the above r e a c t i o n s , the intermediary s a l t has not been previously i s o l a t e d . However, we f i n d that treatment of CpCr(N0) Cl with AgNO^ or AgBF^ in water produces a p r e c i p i t a t e 2 AgCl and a dark green supernatant s o l u t i o n . of the dried reaction mixture i n t o CH^Cl 2 2 2 of Subsequent e x t r a c t i o n followed by c r y s t a l l i z a t i o n from CH Cl /hexanes y i e l d s the CpCr(N0) N0 and CpCr(N0) BF 2 nitrate 3 2 4 compounds as stable green s o l i d s which are soluble i n most organic solvents except hydrocarbons. CH C12 d i s p l a y n i t r o s y l 2 Their i n f r a r e d spectra i n s t r e t c h i n g absorptions at 1841 and 1738 c m " , and 1 at 1848 and 1744 cm" f o r the N 0 " and BF^" s a l t s r e s p e c t i v e l y . These 1 3 absorptions are s i m i l a r to those displayed by [ C p C r ( N 0 ) ] [ A l C l ] " + 2 and are consistent with reduced Cr(diO to N(pir*) donation. 4 (111) However, present attempts to perform the same reaction with the molybdenum complex proceeded with gas evolution and attendant decomposition. - 66 - 4.3c Bis[(n -cyclopentadienyl)ethoxonitrosylchromium], [CpCr(NO)(0Et)] , 5 2 and bis[ch1oro(n -cyclopentadieny1)nitrosylchromium, [CpCr(NQ)C1] . 5 2 When CpCr(N0) C1 i s treated with NaOEt in EtOH or with LiOEt 2 in THF, the CpCr(N0) 0Et can be i s o l a t e d as an unstable red o i l . Its 2 i n f r a r e d spectrum in EtOH d i s p l a y s absorptions at 1792 and 1685 c m , - 1 which are s i g n i f i c a n t l y lower than those of the chloro complex ( i . e . 1812 and 1708 c m -1 i n EtOH) due to the greater e l e c t r o n donating a b i l i t y of the alkoxide l i g a n d . Upon exposure to high vacuum at room temperature, CpCr(N0) (0Et) spontaneously loses n i t r i c oxide to form 2 the new o l i v e green s o l i d , [CpCr(NO)(0Et)] » according to eq. 20. This 2 2CpCr(N0) (0Et) 2 [CpCr(NO) ( 0 E t ) ] 2 + 2N0 20. same transformation can be effected by the e l u t i o n of a CH C1 2 the d i n i t r o s y l compound through an alumina column. 2 s o l u t i o n of The dimeric s p e c i e s , i d e n t i f i e d by elemental a n a l y s i s and mass spectrometry, contains in i n f r a r e d spectrum a s i n g l e terminal n i t r o s y l absorption at 1660 c m C H C 1 , s i m i l a r to the p r e v i o u s l y reported [CpCr(N0)L] 2 2 and SMe) compounds (87, 88). 2 its -1 in (L = NMe , SPh 2 The [CpCr(NO)(OEt)] complex i s soluble in most organic solvents and can be handled i n a i r f o r short periods of time without noticeable decomposition. It decomposes without melting at 233°C, under n i t r o g e n . On the other hand, the s i m i l a r reactions of the molybdenum and tungsten chloro compounds with the above reagents y i e l d only reddish o i l s s i m i l a r in appearance to CpCr(N0) (0Et). 9 A comparison of t h e i r infrared - 67 - spectra with those of the s t a r t i n g chloro complexes, given in the Experimental section and in Table V, suggests that these compounds can be formulated as CpM(N0) (0Et). 2 They possess a remarkable thermal s t a b i l i t y since heating to 95°C under vacuum f o r two hours e f f e c t s no change. A l s o , the attempted dimerization on an alumina column resulted only in complete decomposition, and a n a l y t i c a l l y pure samples of the d i n i t r o s y l s cannot be obtained. The CpM(N0) L (L = SBu, NPh and NH ) 2 2 2 complexes are prepared s i m i l a r l y and they e x h i b i t a behavior s i m i l a r to the ethoxide d e r i v a t i v e s . (L = I, A v a r i e t y of [CpMo(N0)L] and [CpMo(N0)L 1 2 2 2 SPh, SCH Ph and C0 R.p) have been reported but they are obtained 2 from [CpMo(N0)I ] 2 2 2 rather than CpMo(N0) Cl (95-97). 2 The r e a c t i o n of [CpCr(NO)(0Et)] 2 with gaseous HC1 in benzene affords the novel green [CpCr(N0)C1] complex i n high y i e l d , according to 2 eq. 21. Without making any i m p l i c a t i o n s as to the mechanism, t h i s conversion [CpCr(N0)(0Et)] 2 + 2HC1 >- [CpCr(N0)C1] + 2EtOH 21. 2 can be considered as an acid-base reaction between H and O E t " , and i n + p r i n c i p l e , a s i m i l a r transformation should occur with any acid stronger than EtOH. As expected, the s u b s t i t u t i o n of the ethoxide group by the c h l o r i d e anion causes the terminal n i t r o s y l from 1660 to 1678 c m " . 1 s t r e t c h i n g frequency to increase Like [CpCr(NO)(0Et)] , the chloro d e r i v a t i v e 2 is very soluble i n common organic solvents except hexanes and, though stable in a i r for short periods of time, i s best stored under n i t r o g e n . The structures of [CpCr(NO)(0Et)] 2 and [CpCr(N0)C1] expected to be s i m i l a r to those of [CpCr(NO)(SPh)] 0 (91) and 2 are - 68 - [CpCr(MO)(NMe )] 2 2 (92), which are characterized by symmetrically bridging SPh and NMe ligands and by a d i s t i n c t metal-metal bond. Both the trans 2 and c i s forms, D and E, can be i s o l a t e d . A l s o , the s t r u c t u r e of D Cp Cr (N0) (NH ) shows a trans arrangement containing both n i t r o s y l and 2 2 2 2 amido bridges (94). The Cr-N linkages of the t e r m i n a l l y coordinated n i t r o s y l groups have considerable double bond c h a r a c t e r , while the Cr-N-0 bond angles are approximately 170°, as they are a l s o in CpCr(N0) Cl and 2 CpCr(N0) (NC0) (106, 107). 2 The dimeric nature of [CpCr(NO)(0Et)] 2 and [CpCr(N0)Cl] confirmed by t h e i r mass spectral d a t a , shown in Table X I . 2 is The fragmen- t a t i o n p a t t e r n s , i n d i c a t i n g the l o s s of NO, e t h y l , ethoxo, chloro and Cj-H fragments, are s i m i l a r to those found i n the mass spectra of 5 [CpMo(N0)I] 2 and [CpMo(NO)(SCH Ph)] , i n which the parent ions are a l s o 2 r e l a t i v e l y abundant (95). 2 In the mass spectra of both the chloro and ethoxo complexes the i n t e n s i t y pattern at m/e = 182 i s i n d i c a t i v e of [ C p C r ] 2 rather than the [ ( C H ) C r ] 3 3 2 2 + or [CpCr(N0)C1] fragments. The same + assignment has been made i n the cases of [CpCr(NO)(SMe)] (88) and 2 Cp Cr (N0)^(NH ) (89), 9 9 9 where [ C p C r ] 9 + i s thought to a r i s e from the + - 69 - Table XI. Low Resolution Mass Spectral Data f o r [CpCr(N0)(0Et)] [CpCr(N0)Cl] 2 0.4 Cp Cr Cl (N0) 2 334 3.3 Cp Cr Cl (N0) 2 304 3.4 Cp Cr Cl 182 10.0 152 2.9 CpCrCl 117 3.1 CpCr 52 2.3 Cr 384 0.6 Cp Cr (0Et) (N0) 354 6.8 Cp Cr (0Et) (N0) 324 10.0 Cp Cr (0Et) 295 1.5 Cp Cr (0Et)0 279 1.7 Cp Cr (0Et) 250 2.1 Cp Cr 0 182 6.4 Cp Cr 162 1.4 CpCr(0Et) 117 0.9 CpCr 52 1.4 Cr a 2 2 2 2 2 2 2 2 2 + 2 + 2 Assignment 364 Assignment 2 2 Relative Abundance Relative Abundance 2 a m/e m/e 2 [CpCr(N0)X] + + 2 + 2 2 2 2 2 2 ^ C r and J 0 2 + 2 + + + + + + The assignments involve the most common n a t u r a l l y occurring i.e. + 2 2 Cp Cr 2 C1. isotopes, - 70 fragmentation of the metastable [Cp2Cr2$2] and [Cp2Cr2(NH2)] + + species respectively. 4.3d The a l k y l - and ary1-(n -c,yclopentadienyl ) d i n i t r o s y l 5 complexes of chromium, molybdenum and tungsten, CpM(N0)pR (M = C r , Mo or W; R = a.l kyl or a r y l ) . These complexes are obtained in reasonable y i e l d s by the reaction of the corresponding C p M ^ O ^ C l compounds with the appropriate organoaluminum reagent according to the general eq. 2 1 , CpM(N0) Cl + R - A l ^ 2 b - £ ! l ^ j £ ^ CpM(N0) R + C l - A l ^ r H 5 where M = C r , Mo or W and R = a l k y l or a r y l . 2 21. During the course of the r e a c t i o n an o i l y red-brown s o l i d of undetermined composition i s d e p o s i t e d , and the exact nature of the aluminum byproduct remains to be a s c e r t a i n e d . This synthetic procedure appears to be quite general f o r the chromium and molybdenum compounds and i s l i m i t e d only by the a v a i l a b i l i t y of the appropriate A l r e a g e n t . However, i n the case of tungsten, only the phenyl and methyl d e r i v a t i v e s are o b t a i n e d , the l a t t e r only a f t e r a prolonged r e a c t i o n time. Treatment of C p l ^ N O ^ C l with Et^Al or AlH(i-Bu)2 under various reaction conditions f a i l s to give the expected a l k y l a t e d products. Interestingly, in the reactions i n v o l v i n g A l H ( i - B u ) 2 only the i-Bu group, rather than the hydride, i s t r a n s f e r r e d to the metal. The Me, Et and Ph d e r i v a t i v e s of chromium were p r e v i o u s l y reported (27) but are obtained here in better y i e l d s . The remaining a l k y l - 71 - and a r y l complexes were unknown p r i o r to t h i s work. The physical properties of these complexes are summarized i n Tables VII and V I I I . A l l the complexes are very soluble i n organic sol v e n t s , i n c l u d i n g hexanes, and may be exposed to a i r f o r short periods of time without decomposition. Those compounds which are s o l i d s at room temperature _q sublime r e a d i l y at 30-40°C (5 x 10 mm) without decomposition and a r e , indeed, best p u r i f i e d i n t h i s manner. However, the ones which are l i q u i d s a t room temperature decompose slowly under nitrogen but may be stored f o r many months a t -5°C or lower. The methyl and phenyl d e r i v a - t i v e s , e s p e c i a l l y those of chromium, are the most thermally stable and melt without decomposition. The i n f r a r e d spectra (Table V I I I ) of a l l the complexes d i s p l a y two strong a b s o r p t i o n s , s i m i l a r to those in CpM(N0) Cl, due to terminal 2 n i t r o s y l N-0 s t r e t c h i n g s . As expected, these s t r e t c h i n g frequencies decrease i n the order Cl > Ph > a l k y l which p a r a l l e l s the a b i l i t y of these ligands to withdraw e l e c t r o n i c charge from the c e n t r a l metal. The proton NMR spectra (Table V I I I ) e x h i b i t a sharp s i n g l e t f o r the C^Hg protons as well as the expected patterns and i n t e g r a t i o n f o r the a l k y l and a r y l protons. ratios Not too s u r p r i s i n g l y , the p o s i t i o n of the Cp resonance remains nearly independent of the c h l o r o , a l k y l or a r y l substituent present f o r any given metal. Any e l e c t r o n i c perturbation about the central metal i s buffered by the presence of the strong T T accepting n i t r o s y l l i g a n d s . In f a c t , the N-0 s t r e t c h i n g frequencies do vary s i g n i f i c a n t l y , as mentioned, and hence provide a more s e n s i t i v e measure f o r detecting changes i n e l e c t r o n i c d i s t r i b u t i o n around the central Figure2. *H N M R of (T7 -C H )MO(N0) CH CH 5 5 5 2 2 3 Experimental spectrum T I 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 " 1 1 1 1 1 1 1 1 1 1 1 1 1 1 r 1 1 1 r - 73 - metal. The presence of the a-bonded ethyl group in CpMo(N0) Et i s 2 unequivocally demonstrated by the computer f i t t i n g of the A B 2 3 multiplet due to the a l k y l proton resonance, from which the f o l l o w i n g parameters can be extracted (Figure 2 ) : x(CH ) 2 8.10, T(CH ) 3 8.26, J(CH , 2 CH ) 3 7.54 Hz^. The mass spectral data for each complex in Table XII the molecular ion as the highest-mass fragment. exhibit The fragmentation patterns f o r the Et and i-Bu d e r i v a t i v e s of molybdenum are s i m i l a r , but assignments are complicated by concomitant fragmentation of the a l k y l groups and by the large number of molybdenum i s o t o p e s . The most s t r i k i n g d i f f e r e n c e between the phenyl and methyl complexes i s the systematic absence of the [CpM(N0)] and [CpM(N0) ] + + 2 fragments in the phenyl compounds, and the absence of [ ( C H ) M R ] and [CpMR] i n the methyl d e r i v a t i v e s . + 3 + 3 These data strongly suggest that the metal-carbon bond i s stronger in the phenyl than in the methyl compounds, and that the trend i s independent of the metal. The major d i f f e r e n c e among the metals i s that the chromium- containing complexes show an abundance of C r + and [ C p C r ] + fragments whereas, f o r the molybdenum- and tungsten-containing analogs, the c o r r e s ponding fragments are much l e s s abundant. The two most general preparative routes to a-bonded a l k y l and a r y l complexes involve the n u c l e o p h i l i c displacement of the halide from e i t h e r the t r a n s i t i o n metal complex, eq. 22, or from an a l k y l or a r y l h a l i d e , We thank Ms. V. Gibb f o r assistance in obtaining these s p e c t r a . Table XII. Mass Spectral Fragmentation Data f o r CpM(N0) R. 9 . b ion Compound M + C 5 5 H M + C H M(N0) 5 5 + C H M(N0) 5 5 + 2 C 3 3 H M R + C H MR 5 5 + C H M(N0)R 5 5 + C H M(N0) R 5 5 10.0 8.3 - - - 2.3 7.5 0.7 - - - - 2.7 3.6 8.2 3.6 CpW(N0) C H - - .1-7 - - 4.2 7.2 10.0 5.6 CpCr(N0) CH 3 10.0 8.4 2.7 1.2 - 2.1 7.2 1.6 CpMo(N0) CH 3 5.7 3.6 10.0 6.2 - - 6.2 6.0 3 0.4 - 2.9 3.4 - - 4.6 6.2 CpCr(N0) Et 10.0 2.7 1.9 2.0 - 1.9 5.6 0.4 CpCr(NO) i-Bu 10.0 9.9 3.5 4.1 7.2 - 9.9 2.9 CpCr(N0) C H 5 CpMo(N0) C H 5 2 g 2 2 6 g 5 2 2 CpW(N0) CH 2 2 2 + 2 Entries i n t h i s t a b l e are r e l a t i v e ion i n t e n s i t i e s with the most intense metal containing ion assigned an a r b i t r a r y value of 10.0 R e l a t i v e i n t e n s i t i e s were evaluated by measuring peak heights corresponding to the most abundant isotope of each metal: 5 2 Cr, 98 M o and 1 8 4 W. Only unambiguously assignable ions are g i v e n ; f o r the p o l y i s o t o p i c molybdenum and tungsten overlapping of some medium to strong i n t e n s i t y peaks i n the lower mass range made assignments d i f f i c u l t . Selected compounds were run on the MS902 high r e s o l u t i o n instrument which measured exact masses of a l l major peaks; c a l c u l a t e d and measured values were in good agreement. - 75 - eq. 23, (112). The synthetic route given by eq. 23 cannot be e x p l o i t e d L M-X + R-M is— L MR + M'X 1 n (M 1 22. n = Li or MgX) [ L M ] " + R-X » - L MR + X" n 23. n in t h i s instance since a l l attempts to obtain the [ C p M ^ O ^ ] " anions have thus f a r f a i l e d . Indeed, the only well c h a r a c t e r i z e d organometallic n i t r o s y l anion which has been s u c c e s s f u l l y used as a synthetic precursor i s [Fe(C0) (N0)]" (53, 113, 114). 3 While eq. 22 has been applied with modest success in the p r e p a r a t i o n ' o f C p C r ^ O ^ R (R = Me, Et or Ph) (27), the s i m i l a r reactions of C p M ^ O ^ C l (M = Mo or W) with various alkyllithium and Grignard reagents f a i l to y i e l d even s p e c t r o s c o p i c a l l y detectable q u a n t i t i e s of the corresponding a l k y l or a r y l d e r i v a t i v e s . These reagents are not s u f f i c i e n t l y s e l e c t i v e in the n u c l e o p h i l i c displacement of the halide and they appear to attack other f u n c t i o n a l groups. In c o n t r a s t , we f i n d the organoaluminum reagents to be p a r t i c u l a r l y mild and s e l e c t i v e in t h e i r reactions with C p M ^ O ^ C l complexes. This feature i s a l s o i l l u s t r a t e d by the e x c l u s i v e monoalkylation of some d i c h l o r o compounds of ruthenium even when an excess of the organoaluminum reagent i s used at elevated temperatures (115). Organoaluminum compounds are r e l a t i v e l y strong Lewis acids which are known to coordinate to the oxygen end of carbonyl ligands i n a v a r i e t y of neutral complexes. (116) and anionic (117) n -cyclopentadienylmetal carbonyl 5 Non-bonding e l e c t r o n p a i r s l o c a l i z e d on the metal atom may also - 76 - serve as a Lewis base s i t e and a number of 1:1 adducts containing the M-Al bond have been i s o l a t e d (118). However, no i n f r a r e d spectroscopic evidence was obtained in support of any s i m i l a r Lewis acid-base adducts during our preparation of the C p M ^ O ^ R complexes. Although useful in the syntheses of main group metal a l k y l and a r y l compounds (119), the organoaluminum reagents have received very l i t t l e a t t e n t i o n i n the formation of t r a n s i t i o n metal-carbon bonds (112). The general r e a c t i o n of organoaluminum compounds with metal halides (eq. 24) R-Al + M-X *~ A l - X + M-R 24. i s favored when M i s s u b s t a n t i a l l y e l e c t r o p o s i t i v e and X i s e l e c t r o n e g a t i v e . The conversion does not l i k e l y take place by a d i s s o c i a t i v e and r e a s s o c i a t i v e i o n i c pathway since the organoaluminum compounds are l a r g e l y covalent. A l s o , the reactions are t y p i c a l l y performed i n solvents which do not support i o n i z a t i o n and, indeed, the use of coordinating solvents or the presence of Lewis bases retard the r e a c t i o n . Consistent with the above f a c t s , the present a l k y l a t i o n reactions can be considered to occur v i a a Lewis acid-base intermediate as in III or IV, where M i s an organo- metallic residue. R M X X EZ + - 77 - If M i s s u f f i c i e n t l y e l e c t r o p o s i t i v e , as i s the case with the a l k a l i metals, III and IV are formed as stable products rather than intermediates (119). Since the CpM(N0) Cl complexes d i s p l a y a c e r t a i n 2 i n c l i n a t i o n to form the c a t i o n i c [CpM(N0) ] + 2 s p e c i e s , the benzene i n s o l u b l e byproduct deposited during the syntheses of CpM(N0) R may 2 reasonably be formulated as [CpM(N0) ] 2 + [AlR^Cl]". However, t h i s p o s s i b i l i t y was not i n v e s t i g a t e d . In contrast to the numerous CpCr(N0) R complexes, the only known 2 i s o e l e c t r o n i c t r i c a r b o n y l analog i s the thermally unstable CpCr(C0) Me' 3 compound. However, the CpM(C0) R (M = Mo or W) compounds are more 3 abundant and have been the subject of considerable study. Notably, these complexes undergo a thermal transformation to y i e l d [CpM(C0) ] 3 (120, 121) or, when R = E t , Ph or CHpPh, [RC H M(C0) 1 5 4 3 2 (121, 122). 2 Our attempts to obtain s i m i l a r l y the analogous, but as yet unknown, [CpM(N0) ] 2 2 (M = Mo or W) dimers by the thermolysis of the a l k y l - or a r y l d i n i t r o s y l complexes have been u n s u c c e s s f u l . Moreover, the n i t r o s y l complexes are understandably more i n e r t toward s u b s t i t u t i o n than the i s o e l e c t r o n i c CpM(C0) R analogs, and no r e a c t i o n p a r a l l e l to carbonyl " i n s e r t i o n " has 3 yet been found. On the other hand, both CpCr(N0) R and CpM(C0) R undergo 2 3 i n s e r t i o n of S 0 a f f o r d i n g d e r i v a t i v e s which contain the S - s u l f i n a t e 2 l i n k a g e , M-'s'-R (123-125). 8 The rates of i n s e r t i o n into the n i t r o s y l containing complexes a r e , by f a r , the greatest among the v a r i e t y of compounds studied (126). Infrared spectroscopic evidence (127) and k i n e t i c studies (126) i n d i c a t e that S 0 i n s e r t i o n occurs with the 9 initial - 78 - II formation of the O - s u l f i n a t e linkage M-OSR followed by rearrangement to the S - s u l f i n a t e compound. S i m i l a r l y , (CN) C=C(CN) reacts with the 2 above carbonyl and n i t r o s y l 2 complexes to give the d i r e c t insertion product, MC(CN) C(CN) R, and the keteniminato d e r i v a t i v e , MN=C=C(CN)C(CN) R 2 2 2 (124, 128). Stannous c h l o r i d e and bromide i n s e r t i n t o the metal-carbon bond a l k y l c a r b o n y l ( n - c y c l o p e n t a d i e n y l ) m e t a l complexes (M-R) of a v a r i e t y of 5 to y i e l d MSnRX , MSnX^ and MX, depending on r e a c t i o n conditions (129). 2 We f i n d that reaction of S n C l of CpMo(N0) Cl e x c l u s i v e l y . 2 2 with CpMo(N0) i-Bu r e s u l t s i n the formation 2 However, S n C l 2 does i n s e r t i n t o the metal- c h l o r i n e bond of CpCr(N0) Cl according to the solvent dependent e q u i l i b r i u m , 2 eq. 25. In donor solvents such as THF the l e f t hand side of eq. 25 i s CpCr(N0) Cl + SnCl =^===^== CpCr(N0) SnCl 2 2 2 25. 3 favored probably due to Lewis acid-base i n t e r a c t i o n between S n C l s o l v e n t , whereas CH C1 2 CpCr(N0) SnCl 2 1825 c m - 1 and benzene s h i f t the e q u i l i b r i u m to the side of 2 The i n f r a r e d n i t r o s y l 3 i n CH C1 ) of CpCr(N0) SnCl 2 and the 2 2 2 s t r e t c h i n g frequencies (1733 and are approximately 20 c m 3 -1 higher than those of C p C r ( N 0 ) C l , which we a t t r i b u t e to the p r e v i o u s l y demonstrated 2 poorer o-donating and stronger ^-accepting properties of the SnCl^ entity 4.3e (26a). Bis[(n -cyclopentadienyl)dinitrosylchromium], [CpCr(N0) ]Q, 5 2 When a benzene s o l u t i o n containing CpCr(N0) Cl i s allowed to 2 s t i r over a sodium amalgam, [ C p C r ( N 0 ) ] 9 o i s obtained i n over 60% y i e l d . - 79 - This synthetic route i s f a r superior to the one previously reported in which the desired product i s extracted in only 5% y i e l d (90). The same conversion can be effected by using a zinc amalgam and, to a l e s s e r e x t e n t , with f i n e l y divided magnesium or ytterbium metal although a much longer reaction time i s necessary. In these l a t t e r reactions no evidence i s obtained f o r the existence of a c t i v a t e d species (105) such as "CpCr(N0) MgCl". When f i n e l y divided z i n c metal i s employed, no 2 reaction occurs and the use o f a magnesium amalgam in THF causes immediate decomposition of the s t a r t i n g chloro complex. Correspondingly, the attempted reduction of the CpM(N0) Cl (M = Mo or W) compounds using 2 a wide v a r i e t y of reaction conditions f a i l s to y i e l d the s t i l l [CpM(N0) ] 2 2 unknown (M = Mo or W) complexes. The o r i g i n a l synthesis of [ C p C r ( N 0 ) J from CpCr(N0) Cl and 2 2 2 NaBH^ i s believed to occur through the formation of CpCr(N0) H although 2 no evidence f o r t h i s hydrido intermediate was obtained (90). However, we f i n d that CpMo(N0) Cl reacts with NaBH^ i n MeOH or EtOH at -30°C to y i e l d 2 a v o l a t i l e pale-green s o l i d which decomposes r a p i d l y at room temperature. Its i n f r a r e d spectrum (1740 and 1645 cm" i n EtOH) bears a s t r i k i n g 1 resemblance to those of the a l k y l and a r y l d e r i v a t i v e s , and on t h i s basis the complex i s formulated as CpMo(N0) H. The thermal or o x i d a t i v e 2 degradation of t h i s s p e c i e s , e i t h e r in s o l u t i o n or i n the s o l i d , f a i l s to provide the [CpMo(N0) J compound. 2 2 The i n f r a r e d spectrum of [ C p C r ( N 0 ) ] 2 2 e x h i b i t s two strong n i t r o s y l absorptions at 1667 and 1512 cm" i n CH^Cl > i n d i c a t i v e of both 1 2 terminal and bridging n i t r o s y l ligands. In CDCl^ s o l u t i o n s the dimer e x i s t s i n both the c i s and trans forms, F and G, as evidenced by i t s - 80 - F G room temperature proton NMR which contains two sharp s i n g l e t s at T5.20 and T5.00 i n the r a t i o of 1:20 (93). (93), In the s o l i d s t a t e , [ C p C r ( N 0 ) l 2 i s i s o s t r u c t u r a l with t r a n s - [ C p F e ( C 0 ) o ] [CpCr(N0)(SPh)] 2 (91) 2 2 (130), t r a n s - and trans-[CpCr (NO) ( N H j ] , , (92). The metal-metal o distance of 2.615 A in the d i n i t r o s y l dimer i s s i g n i f i c a n t l y shorter than those of the SPh (2.90 A) and NH (2.67 A) containing s p e c i e s . While 2 the terminal Cr-N-0 bond angles in the SPh and NH compounds deviate 2 from l i n e a r i t y by about 1 0 ° , ' t h e corresponding angle in the d i n i t r o s y l species i s v i r t u a l l y l i n e a r ( 1 7 6 . 6 ° ) , p o s s i b l y as a r e s u l t of reduced e l e c t r o n density on the metal atoms of the n i t r o s y l bridged compound. The terminal Cr-N bond lengths f o r a l l three dimers f a l l w i t h i n the range of o o 1.64-1.69 A and are not much d i f f e r e n t from the value of 1.71 A in the CpCr(N0) Cl compound (106). 2 As expected, the Cr-N distance (1.960 A) in the symmetrically-bridging n i t r o s y l ligands i s considerably longer than the terminal Cr-N bonds. The mass spectrum of [ C p C r ( N 0 ) l 2 2 (Table X I I I ) d i s p l a y s the molecular ion peak and i s c o n s i s t e n t with the dimeric f o r m u l a t i o n . no [CpCr(N0) ] n or [C^H^Cr(N0) ] n (n = 1 or 2) fragments are formed, Since it - 81 - Table X I I I . Low Resolution Mass Spectral Data f o r [CpCr(N0) ] 9 9 m/e Relative Abundance 354 3.1 Cp Cr (N0) 4 324 2.2 Cp Cr (N0) 3 294 0.3 Cp Cr (N0) 2 264 10.0 Cp Cr (N0) 182 6.1 (C H ) Cr 117 2.3 CpCr 52 4.2 Cr The assignments involve the most common n a t u r a l l y 52 i.e. Cr. r Assignment 2 2 2 2 2 2 2 + + + + 2 3 3 2 + 2 + + occurring isotope, - 82 - appears that fragmentation prefers to occur without rupture of the metal-metal bond. In c o n t r a s t , the i s o e l e c t r o n i c non-bridged [CpCrv^CO)^] dimer does not d i s p l a y a molecular ion peak and, indeed, only mononuclear fragments are found (131). Unlike [ C p C r ( N 0 ) ( 0 E t ) ] contrary to a previous report [CpCr(N0) ] 2 [Cp Cr] 2 + 2 2 or [CpCr(N0)C1] , and 2 (89), we f i n d that the mass spectrum of does not contain a peak which may be assigned to the fragment. Instead we assign the peak at m/e = 182 to the d i n u c l e a r [ ( C ^ H ^ ^ C r ^ * fragment. Furthermore, the greater abundance of dinuclear species i n the mass spectrum of [ C p C r ( N 0 ) l suggests that 2 the n i t r o s y l 2 ligand forms a stronger bridge than do the OEt or Cl ligands in r e l a t e d compounds. - 83 - CHAPTER V Conclusion It should be stressed that while m e t a l - n i t r o s y l bonds may be formed by a v a r i e t y of synthetic methods,' none o f these preparative routes has general a p p l i c a b i l i t y . In c o n t r a s t , t h i s work has shown n i t r o s y l c h l o r i d e to be the s i n g l e most v e r s a t i l e s y n t h e t i c reagent a v a i l a b l e for the formation of M-NO l i n k a g e s . The d i r e c t formation of c h l o r o n i t r o s y l complexes from neutral carbonyl compounds i s of p a r t i c u l a r interest. As discussed in t h i s t h e s i s , the former compounds, which contain a very r e a c t i v e m e t a l - c h l o r i n e bond, serve as useful precursors in the preparation of f u r t h e r n i t r o s y l d e r i v a t i v e s . For example, the metal-halide bond may be converted to a large v a r i e t y of metal-heteroatom a-bonds containing elements from Groups IVA, VA and VIA. Obviously, the behavior of n i t r o s y l c h l o r i d e with many more neutral and anionic metal carbonyl complexes remains to be i n v e s t i g a t e d . Most importantly, such studies should be undertaken with the aim of developing convenient synthetic routes to n i t r o s y l complexes, and not simply as a study of the chemistry o f n i t r o s y l chloride. The s c a r c i t y of anionic n i t r o s y l complexes i s s u r p r i s i n g , e s p e c i a l l y in view of the multitude of anionic carbonyl compounds which - 84 - has been c h a r a c t e r i z e d . of various n i t r o s y l While attempts to e f f e c t the chemical reduction compounds have so f a r been u n s u c c e s s f u l , n i t r o s y l - containing anions might be obtained by electrochemical reduction at a controlled potential. Further work in t h i s d i r e c t i o n i s c u r r e n t l y in progress. While numerous n i t r o s y l compounds are known, many, which are expected to be stable under ambient c o n d i t i o n s , are simply nonexistent at present. 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