* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download NICKEL(II) PINCER COMPLEXES SUPPORTED BY 2,6
Theory of solar cells wikipedia , lookup
Geochemistry wikipedia , lookup
Jahn–Teller effect wikipedia , lookup
Oligonucleotide synthesis wikipedia , lookup
Artificial photosynthesis wikipedia , lookup
Asymmetric hydrogenation wikipedia , lookup
Asymmetric induction wikipedia , lookup
Drug design wikipedia , lookup
Crystallographic database wikipedia , lookup
Transition state theory wikipedia , lookup
Electrochemistry wikipedia , lookup
Click chemistry wikipedia , lookup
Biochemistry wikipedia , lookup
Physical organic chemistry wikipedia , lookup
Hydrogen-bond catalysis wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
Multi-state modeling of biomolecules wikipedia , lookup
Crystallization wikipedia , lookup
Photoredox catalysis wikipedia , lookup
Aromatization wikipedia , lookup
Hypervalent molecule wikipedia , lookup
Nickel (United States coin) wikipedia , lookup
Supramolecular catalysis wikipedia , lookup
Crystal structure wikipedia , lookup
Inorganic chemistry wikipedia , lookup
Cooperative binding wikipedia , lookup
Evolution of metal ions in biological systems wikipedia , lookup
Enantioselective synthesis wikipedia , lookup
Discodermolide wikipedia , lookup
Lewis acid catalysis wikipedia , lookup
IUPAC nomenclature of inorganic chemistry 2005 wikipedia , lookup
Strychnine total synthesis wikipedia , lookup
Stille reaction wikipedia , lookup
Metalloprotein wikipedia , lookup
Metal carbonyl wikipedia , lookup
Ligand binding assay wikipedia , lookup
Hydroformylation wikipedia , lookup
Coordination complex wikipedia , lookup
NICKEL(II) PINCER COMPLEXES SUPPORTED BY 2,6-BIS(3,5-DITOLYL-2PYRROLYL)PYRIDINE by ABHIJIT PRAMANIK Presented to the Faculty of the Graduate School of The University of Texas at Arlington in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE IN CHEMISTRY THE UNIVERSITY OF TEXAS AT ARLINGTON May 2015 Copyright © by Abhijit Pramanik 2015 All Rights Reserved ii Acknowledgements I would like to acknowledge the contribution of the following persons to the fulfillment of this thesis work. I am specially thankful to my supervising professor Dr. H. V. Rasika Dias for his guidance and encouragement through my graduate study at UT Arlington. I also would like to thank the other committee members, Dr. Alejandro Bugarin and Dr. Brad Pierce for their support. I am thankful to Dr. Muhammed Yousufuddin for his Xray crystallography work. I appreciate the immense help I received from all other past and present Dias research group members. I would like to mention the names of some lab members like Dr. Chandrakanta Dash, Dr. Animesh Das, Dr. Naveen Kulkarni, Mr. Venkata K. Adiraju, Mr. Naleen Jayaratna for their assistance in learning the theoretical and technical skills needed for my research. Finally, I would also like to thank the Department of Chemistry and Biochemistry of The University of Texas at Arlington, the Robert A. Welch Foundation and National Science Foundation for their financial support. April 14, 2015 iii Abstract NICKEL(II) PINCER COMPLEXES SUPPORTED BY 2,6-BIS(3,5-DITOLYL-2PYRROLYL)PYRIDINE Abhijit Pramanik, MS The University of Texas at Arlington, 2015 Supervising Professor: H. V. Rasika Dias Ni(II) pincer complexes are among the most important and useful compounds in homogeneous catalysis. Significant advancement has been made in this field in recent years. Many Ni(II) pincer complexes have been prepared and utilized in various catalytic reactions e.g. cross coupling reactions, C-H activation, carbon dioxide activation etc. Still, nickel(II) complexes supported by the pincer ligand with three nitrogen donors are relatively less explored and catalytic applications with those complexes are scarce in literature. This thesis describes the synthesis of a new pyrrolyl pyridine based pincer ligand and its Ni(II) complexes. The pyrrolyl pyridine pincer ligand, a relatively new class of dianionic, tridentate, nitrogen-based ligands in coordination chemistry, was prepared starting with a modified method for the synthesis of pyrrolyl pyridine. This modified procedure is simpler, less time consuming making it cheaper than the classical method and provides 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine in good yields. Reaction of its potassium salt with Ni(OTf)2 resulted in three different stable nickel(II) pincer complexes. 1 The novel nickel(II) pincer complexes were fully characterized by H NMR spectroscopy, 13 C NMR spectroscopy, infrared spectroscopy and high resolution mass spectrometry. The X-ray crystal structures of the new ligand and metal complexes have been described. iv Table of Contents Acknowledgements .............................................................................................................iii Abstract .............................................................................................................................. iv List of Illustrations ..............................................................................................................vii List of Tables………………………………………………………………………………...……ix Chapter 1 NNN pincer ligand………………………………………………………..………….1 1.1 Introduction………………………………………………………………………………..1 1.1.1. Importance of pincer ligands……………………………………………………….1 1.1.2 Brief history of pincer lignads………………………………………………………3 1.1.3 Synthesis of pyrrolyl pyridine pincers………………………………….………….4 1.2 Result & Discussion………………………………………………………………………8 Chapter 2 Ni(II) complexes supported by 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine ligand……………………………………………………………………………………………..12 2.1 Introduction……………………………………………………………………………..12 2.1.1 Significance of nickel chemistry…………………………………………………12 2.1.2 Applications of nickel(II) pincer complexes……………………………………13 2.2 Nickel(II) acetonitrile complex supported by 2,6-bis(3,5-ditolyl-2pyrrolyl)pyridine.................................................................................................................16 2.3 Nickel(II) carbonyl complex supported by 2,6-bis(3,5-ditolyl-2pyrrolyl)pyridine…………………………………………………………………………….……19 2.3.1 Introduction………………………………………………………………….……19 2.3.2 Result & discussion………………………………………………………..…….21 2.4 Nickel(II) ammonia complex supported by 2,6-bis(3,5-ditolyl-2pyrrolyl)pyridine……………………………………………………………………………….…24 v 2.4.1 Introduction……………………………………………………………………....24 2.4.2 Result & discussion………………………………………..……………………25 Chapter 3 Conclusion…………………………………………………………………….……..28 Chapter 4 Experimental Details………………………………………………………..………30 4.1 Synthesis of 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine…………………………….30 4.2 Synthesis of LNiCH3CN…………………………………………………...……..31 4.3 Synthesis of LNiCO………………………………………………………………32 4.4 Synthesis of LNiNH3 ………………………………………………………..……33 Appendix A X-ray Data Collection and Selected Bond Distance………………..…………35 Appendix B Selected Spectroscopy Data…………………………………………….………82 References……………………………………………………………………………………….90 Biographical Information………………………………………………………………………..95 vi List of Illustrations Figure 1. General structure of the pincer-type complexes……………………………………2 Figure 2. Complexes with pincer ligands, synthesized by Shaw and coworkers…….…….3 Figure 3. Van Koten synthesis of Pd- and Pt-complexes with (NCN) pincer ligand..….….3 Figure 4. Development of pincer ligands………………………………………………….……4 Figure 5. One step synthesis of 3,5-disubstitued-2-pyridylpyrroles………………….…..….5 Figure 6. Synthesis of 2,6-bis(3,5-diphenylpyrrol-2-yl)pyridine…………………….….…….6 Figure 7. Synthesis of 2,6-bis(3,5-di-methylpyrrol-2-yl)pyridine………………….…………7 Figure 8. Synthesis of 2,6-bis(3,5-di-tert-butylpyrrol-2-yl)pyridine……………….….………7 Figure 9. Synthesis of 2,6-bis(3,5-di-tolylpyrrol-2-yl)pyridine……………………….….…….9 Figure 10. ORTEP diagram of the molecular structure of ligand……………..…….……...11 Figure 11. Nickel pincer complexes prepared by Liang and coworkers…………...….…..14 Figure 12. Nickel pincer complexes prepared by Vivic and coworkers…………….…..….14 Figure 13. Nickel pincer complexes prepared by Inamoto and coworkers………..….…..15 Figure 14. Cross coupling reaction catalyzed by nickel pincer complex……………….…15 Figure 15. Nickel pincer complex used for CO2 reduction prepared by Guan and coworkers…………………………………………………………………………….……….….16 Figure 16. Synthesis of LNiCH3CN……..………………………………………………….….17 Figure 17. ORTEP diagram of the molecular structure of complex……………………..…18 Figure 18. Orbital overlap in carbon monoxide molecule……………………..……..….….20 Figure 19. Orbital overlap in metal carbonyl bond……………………..………..……….….21 Figure 20. Synthesis of LNiCO…………………...……………………………………..……..22 Figure 21. ORTEP diagram of the molecular structure of complex…………………..……23 Figure 22. Synthesis of LNiNH3 …………………………………………...……………….….26 vii Figure 23. ORTEP diagram of the molecular structure of complex……………...………..27 1 Figure 24. H NMR spectrum of 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine (LH2)…….....……83 Figure 25. 13 C NMR spectrum of 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine (LH2)………..…..84 1 Figure 26. H NMR spectrum of LNi(CH3CN)………………………………....…………….85 Figure 27. 13 C NMR spectrum of LNi(CH3CN)……………………………..…..……………86 Figure 28. Infrared spectrum of LNiCO…………………………………………..…..………87 Figure 29. Infrared spectrum of LNiNH3………..………………………………………….…88 viii List of Tables Table 1. Summary of NMR data of LH2, LNiCH3CN, LNiCO, LNiNH3……………………..89 ix Chapter 1 NNN PINCER LIGAND 1.1 Introduction 1.1.1 Importance of pincer ligands The term “catalyst” was first mentioned by Jöns Jacob Berzelius in th the early 19 century when Sir Humphry Davy observed the hastening of the combustion of certain gases in the presence of platinum. Since then, the ability to accelerate chemical transformations under milder conditions with enhanced selectivity has been very important in chemistry. 1-3, 70 Some milestones of the evolution of catalysis include the oxidation of hydrochloric acid to chlorine in the presence of cupric salts impregnated in clay bricks, Ziegler-Natta process for ethylene polymerization, Haber-Bosch process for the production of ammonia, palladium catalyzed cross-coupling reactions and the olefin metathesis reactions. The metal-catalyzed cross-coupling reactions and C-H activation have become significant tools for organic synthesis. 4-9 Intensive research towards the development of new efficient and selective catalysts grew constantly. The ligand of the metal complex catalyst is responsible for the stability and reactivity of the designed catalytic system. The design and amplification of ligands is one of the most crucial part in catalysis development. 10-16 Pincer-type ligands are one of the most extensively used ligands for complexation with transition metals in organometallic chemistry. Pincer ligand systems have a nice feature of tuning the properties of transition metal complexes to enhance the efficiency of the catalytic processes. Pincer ligands have names according to the way, they attach to the metals. Pincer ligands are basically tridentate ligands coordinated to the metal centers with trans-positioned donor groups D (Figure 1). Conventional pincer ligands have an aromatic framework. Donor 1 groups of the ligand can be changed to provide useful steric and electronic properties. 21 17- Y groups can be modified to impact the electronic properties of the ligand. The length of the linkers has an influence on the coordination pocket and spatial arrangement of the pincer ligand. Furthermore, these positions can also be used to control other properties to the metal environment, such as chirality or enhanced rigidity. Remote electronic modifications can be achieved by changing the R group, attached to the backbone of the ligand. Additionally, labile ligands and non-coordinating counter anions increase the efficiency of the metal centers. A general structure of the pincer-type complexes has been illustrated in Figure 1. Figure 1. General structure of the pincer-type complexes Properties of pincer complexes relate to the atoms bonded to the metal center, and in some cases incorporating Y groups as well. For example, the abbreviated name for the general structure in Figure 1 would be DXD or DYXYD. Pincer ligands will be explained with this way in this project. 1-3, 70 The tridentate and planar nature of pincer ligands help to form stable metal complexes. The stability of the complexes provides advantage in catalysis. They can be heated, exposed to aggressive reagents such as acids, bases and oxidants without decomposition. High turnover numbers are common with pincer catalysts. Another important feature of pincer ligands is that ligand properties can be tuned with the change in substituent in the ligand backbone. 22-27 2 Investigation of the details of reaction mechanism and the detection and isolation of catalytic intermediates are executed efficiently with pincer complexes as well. 1.1.2 Brief history of pincer ligands The first transition metal pincer complex was published by the group of Shaw in 1970s. The synthesis and characterization of complexes of Ni-, Pd-, Pt- and 7-9 other metals supported by (PCP) pincer ligand were reported (Figure 2) . Figure 2. Complexes with pincer ligands, synthesized by Shaw and coworkers. Later the synthesis of another (NCN) pincer ligand and its palladium and platinum complexes were reported by van Koten and coworkers. The ligand was lithiated and then it was used as the starting material for the synthesis of Pd- and Ptcomplexes (Figure 3). They also provided X-ray analysis to support the structures. 4 Figure 3. Van Koten synthesis of Pd- and Pt-complexes with (NCN) pincer ligand. After those seminal studies, pincer ligands received a great deal of attention of the organometallic chemists for their different applications, such as, specific 3 bond activation, small molecule activation and group transfer. After Shaw’s pincer, Fryzuk developed a new backbone by changing the PCP platform to PNP platform which 13 combined soft phosphines with a hard π-base such as amido group (Figure 4) . Replacing the carbon by a nitrogen created a more flexible system which has a facial arrangement unlike the meridional geometry of the carbon analogue. Liang and Kaska incorporated a new ligand in the library where the 29 amido and phosphine residues are connected with a bridge . Then, Ozerov and coworkers improved the ligand by adding alkyl substituents instead of aryl substituents on the phosphine 1-3, 70 . Figure 4. Development of pincer ligands 1.1.3 Synthesis of pyrrolyl pyridine pincers Pyrrolyl pyridine pincers were unknown in the last century. 2,6bis(R)pyridine pincer complexes (R = indolyl, azaindolyl) of some divalent transition metals have been published by some groups and are known for their optical properties, and all have conventional k3 pincer connectivity. In fact, the first efficient syntheses of 4 26 one sided pyrrolyl pyridines were reported by McNeill and coworker in 2002 (Figure 5) . They synthesized 3,5-Disubstituted- and 3,4,5-trisubstituted-2-(2-pyridyl)pyrroles efficiently from the condensation of 2-(aminomethyl)-pyridine and 1,3-diones. A (2pyridyl)methylamine was identified as the intermediate in the cyclization reaction. Both of the aliphatic and aromatic substitutions on the pyrrole ring were obtained while synthesizing the one sided pyrrolyl pyridines. Figure 5. One step synthesis of 3,5-disubstitued-2-pyridylpyrroles In the same year 2002, Nagata and Tanaka, reported the synthesis of 27 a diphenyl version of pyrrolyl pyridine . They used 2,6-dicarboxaldehyde, a chalcone (1,3-diphenyl-2-propen-1-one), a thiazolium salt (3-benzyl-5-(2-hydroxyethyl)-4-methylthiazolium chloride) a base (sodium tert-butoxide) and ammonium acetate as starting materials (Figure 6). 5 Figure 6. Synthesis of 2,6-bis(3,5-diphenylpyrrol-2-yl)pyridine Later in 2007, Dara Bridget Williams reported in PhD dissertation at The University of Washington, the synthesis of dimethyl substituted pyrrolyl pyridine (2,6bis(3’,5’-dimethyl-2-pyrrolyl)pyridine) (Figure 7). 68 This version of the ligand was synthesized following the condensation process reported by McNeill and Coworker. Here, acetylacetone was used as chalcone. 6 Figure 7. Synthesis of 2,6-bis(3,5-di-methylpyrrol-2-yl)pyridine While we were working on our project, another version of this type of ligand was reported by Caulton and coworker (Figure 8). They synthesized di tert-butyl substituted pyrrolyl pyridine (2,6-bis(3,5-di-tert-butylpyrrol-2-yl)pyridine) using ditert-butyl acetyl acetone as chalcone. 69 Figure 8. Synthesis of 2,6-bis(3,5-di-tert-butylpyrrol-2-yl)pyridine Based on the above mentioned discoveries and application of nickel(II) pincer complexes in various chemical processes it was realized that this could be a potential area to explore. So, the first plan was to synthesize a new set of ligand, pyrrolyl pyridine [2,6-bis(3,5-di-tolylpyrrol-2-yl)pyridine] that could be used to prepare 7 some nickel(II) pincer complexes, with a modified procedure originally published by Nagata and Kanaka. Details of the synthesis have been depicted in the next section of the dissertation. 1.2 Result & discussion The starting material of the ligand synthesis, 2,6-dicarboxaldehye was prepared from 2,6-dimethanol pyridine through oxidation with SeO2/Dioxane (Figure 9). Then, tolualdehyde was stirred at room temperature for 5 h with 4-methylacetophenone and NaOH in EtOH/H2O to form 1,3-bis(4-tolyl)-2-propen-1-one. Then it was reacted with 2,6-pyridinedicarbaldehyde, 3-benzyl-5-(-hydroxyethyl)-4-methylthiazolium chloride and sodium t-butoxide in ethanol at reflux for 24 h to form 2,6-bis(2,4-ditolyl-1,4dioxobutyl)pyridine. Finally, the intermediate ketone was reacted with NH 4OAc in ethanol at reflux for 24 h to form 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine (LH2). The intermediate ketone could also be synthesized using potassium tert-butoxide in ethanol or triethylamine in dioxane. The intermediate ketone was purified using a silica gel column before proceeding (Rf = 0.2 with hexane/EtOAc = 9/1). Another interesting point is that the intermediate product (2,6-bis(2,4-diphenyl-1,4-dioxobutyl)pyridine) is a 1:1 mixture of two diastereomers. Both diastereomers were collected and used in the next step. 8 Figure 9. Synthesis of 2,6-bis(3,5-di-tolylpyrrol-2-yl)pyridine(LH2) The ligand (LH2) is soluble in polar solvents like acetone and methanol etc. as well as in non-polar solvents like benzene, pentane, etc. The ligand was 1 characterized by NMR specroscopy, H NMR spectrum of ligand in CDCl3 measured at room temperature exhibits a sharp singlet at 2.38 ppm which is corresponding to the 9 four methyl groups on the pyrollyl-phenyl rings. A multiplet observed at 6.57 ppm is assigned to the two pyrollyl ring protons. The aromatic protons are distributed in the range 7.17 – 7.47 ppm and the two NH protons show a broad resonance at 9.56 ppm. The ratio between the methyl groups of the pyrollyl-phenyl rings, pyrollyl ring protons, and the NH protons follow a 6:1:1 pattern supporting the projected structure for the ligand. 13 The C NMR resonances are also coherent with our assignments. Additional evidence about the composition of the ligand was provided by the HRMS studies, a molecular ion peak observed at m/z 571.14 is assigned to the ligand. The molecular structure of the ligand was further confirmed with the help of X-ray analysis. X-ray quality crystals of the ligand were obtained from a concentrated ether solution of ligand and its solid state molecular structure is presented in Figure 10 (The crystal data and refinement details are provided at the chapter 5.1 (Appendix). The X-ray structure reveals that NCCNCCN coordination cavity is nearly o planar (torsion angles N1-C4-C19-N2 = -3.16 and N2-C23-C24-N3 = -12.11 ) with the three donating N atoms (N1, N2 and N3) in a same plane. Interestingly both the pyrroles t are directed exclusively inward, which is in contrast with the Bu substituted, similar molecule reported earlier. The hydrogen bonding between the pyrrole NH groups and the … … pyridine ring nitrogen (N1H N2 = 2.325 and N3H N2 = 2.235 Å) is possibly the reason for an inward rotation of the two pyrrole rings. The two aryl rings of the pyrrole moieties o that are adjacent to the pyridine ring are twisted about 80 from the NCCNCCN plane to reduce the steric interactions. However the aryl rings that are away from the pyridine ring are in the same plane. 10 Figure 10. ORTEP diagram of the molecular structure of ligand (LH2) o Representative bond lengths (Å) and angles ( ). N1-C1 = 1.372(3), N1-C4 = 1.379(3), N2-C19 = 1.341(3), N2-C23 = 1.353(3), N3-C27 = 1.360(3), N3-C24 = 1.380(3), C4-C19 = 1.470 (3), C23-C24 = 1.458 (3), C1-C5 = 1.472(3) Å; C1-N1-C4 = 110.9 (2), N1-C4-C19 = 116.6 (2), C19-N2-C23 = 119.41(19), N3-C24-C23 = 117.7(2), N1-C4-C19o N2 = -3.16, N2-C23-C24-N3 = -12.11 . 11 Chapter 2 Nickel(II) complexes supported by 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine ligand 2.1 Introduction 2.1.1 Significance of nickel chemistry Our ancestors used nickel long time before its discovery and isolation. In 3500 BC Syrian people used to have a bronze which had a small amount of nickel. th Coins were made in China from nickel in 235 BC. Finally, in the 17 century, German miners found a red coloured ore while searching for copper. After analysis, they came to a conclusion that there was a different material actually present instead of copper. They named it "Kupfernickel" or Old Nick's Copper, which meant false or bad copper. Swedish scientist Baron Axel Frederich Cronsted isolated nickel from an ore in 1751. 28-37 Nickel has a long history in the organometallic chemistry. The first organometallic compound of nickel, nickel carbonyl, Ni(CO) 4 was synthesized in 1890. Nickel has different coordination numbers 2, 3 and 4. Among the three the coordination number 2 is most dominant. Many steric constitution of the ligands is possible in this range e.g. octahedral, trigonal-bipyramidal and tetrahedral etc. 38-41 Nickel is the smallest group 10 metal in the periodic table. It can execute many of the same rudimentary reactions as palladium or platinum. Because of these reasons, nickel is often considered a low-cost replacement catalyst for different cross-coupling reactions. However, there are numerous and diverse nickel catalyzed reactions reported in the literature. Specially, homogeneous nickel catalysis is currently drawing significant attention of the scientists. Here, we will discuss recent developments in homogeneous nickel catalysis as Ni(II) pincers are mostly used as homogenous catalysts. 12 Oxidative addition i.e. loss of electron density occurs easily around nickel. On the other hand, reductive elimination is less likely. Palladium catalysis is less favorable for the oxidative addition that allows the use of cross-coupling electrophiles. Nickel complexes catalyze the reactions of alkenes and alkynes e.g. oligomerization or reductive coupling. While in case of β-Hydride elimination, quite opposite trend can be noticed. Palladium is more efficient in β-Hydride elimination than nickel. Nickel has higher energy barrier than palladium to Ni–C bond rotation prior to β-hydride elimination. 1-5 Nickel is smaller in atomic radius, and usually has shorter Ni–ligand bond lengths. Nickel is roughly 2,000 times cheaper than palladium and 10,000 times cheaper than platinum on a mole-for-mole basis. 1-8 2.1.2 Applications of Nickel(II) pincer complexes Applications of nickel chemistry comprise of materials science, polymer synthesis and biocatalysis, homogeneous and heterogeneous catalysis. However, only application of nickel in homogeneous catalysis will be discussed here as that relates to Ni(II) pincer complexes. Following are some main areas of homogeneous catalysis where Ni(II) pincer complexes are prevalent. Cross-coupling In organic synthesis cross-coupling reactions of organic halides with organometallic reagents catalyzed by transition metals have extensive applications e.g. Kumada, Negishi, Suzuki, and Stille reactions. Both nickel and palladium have been widely used in cross-coupling reactions as efficient catalysts. Saturated as well as unsaturated substrates are known for the same purpose. 13 42-50 In 2006, Liang and co-workers published preparation and catalytic applications of amido-pincer–nickel complexes (Figure 11) for the Kumada coupling of phenyl iodide or bromide with Grignard reagents. 48-50 Figure 11. Nickel pincer complexes prepared by Liang and coworkers Several Ni–terpy complexes that can catalyze the coupling of alkyl iodides with alkylzinc reagents efficiently were reported by Vivic and coworkers (Figure 1-5 12). Figure 12. Nickel pincer complexes prepared by Vivic and coworkers 14 In 2006 Inamoto and co-workers discovered the cross-coupling of aryl bromides and chlorides with phenylboronic acid by NHCbased CNC-pincer–nickel 1-6 complex (Figure 13). Figure 13. Nickel pincer complexes prepared by Inamoto and coworkers Heck reaction In 2006, Sakamoto and Watanabe reported an air- and moisturestable nickel(II) bis-carbene pincer complex (Figure 14) which executes Heck reaction and the Suzuki coupling reaction of a variety of aryl halides with good yields of products. 50 Figure 14. Cross coupling reaction catalyzed by nickel pincer comple 15 Catalytic reduction of CO2 In 2010 Guan and coworker reported a new nickel bis(phosphinite) pincer complex [2,6-(R2PO)2C6H3]NiCl (LRNiCl, R = cyclopentyl) in one pot from resorcinol, ClP(C5H9)2, NiCl2, and 4-dimethylaminopyridine which produces a nickel hydride complex with treatment of LiAlH4 (Figure 15). The nickel hydride complex is able to reduce CO2 rapidly at room temperature to form a nickel formate complex. 54 Figure 15. Nickel pincer complex used for CO2 reduction prepared by Guan and coworkers Considering the significant catalytic efficiency and vast applications of Ni(II) pincer complexes discussed above, the preliminary goal was to synthesize some Ni(II) pincer complexes supported by the above mentioned dianionic pincer ligand, 2,6bis(3,5-ditolyl-2-pyrrolyl)pyridine. 2.2 Nickel(II) acetonitrile complex supported by 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine Synthesis of one LNi(II)CH3CN complex was first attempted as it could be used as starting material for preparation of other complexes (Figure 16). The ligand 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine (LH2) was deprotonated by refluxing it with 1.5 equivalent of KH for 1.5 hrs in dry THF under nitrogen atmosphere. Then the excess KH was removed by filtration under nitrogen. The deprotonated potassium salt of the ligand 16 was never isolated. The potassium salt of the ligand in dry THF was stirred with one equivalent of Ni(OTf)2 overnight. Finally THF was removed and the remaining substance was stirred in acetonitrile for an hour. The NMR spectrum of the substance after removal of solvent wasn’t clean. Besides desired product peaks, some peaks of unreacted ligand and some other unknown peaks were observed. The LNi(II)CH3CN complex was isolated in pure form after crystallization from slow diffusion of hexane vapor through a solution of the complex in acetonitrile. The red crystals diffracted well under X-ray. The structure was confirmed by XRD, NMR and HRMS. But, the (CN) triple bond of the complex didn’t show any significant absorption under Infrared. Figure 16. Synthesis of LNiCH3CN 1 The H NMR data is in consistent with expected molecular structure of the complex LNiCH3CN.The chemical shift values and intensities of the peaks corresponding to the acetonitrile group, methyl groups of the pyrollyl-phenyl rings and pyrollyl ring protons are in line with the projected structure of the complex. The corresponding 13 C NMR signals also correlate with predicted structure of the complex. In the HRMS studies, a molecular ion peak was observed at m/z 666.21, which is in consistent with the molecular formula C43H36N4Ni is assigned to the complex. 17 Figure 17. ORTEP diagram of the molecular structure of complex (LNiCH3CN) o Representative bond lengths (Å) and angles ( ). N1-Ni = 1.896 (2) , N2-Ni = 1.844 (2) , N3-Ni = 1.906 (2), N4-Ni = 1.862 (3), N1C4 = 1.398 (4) , N2-C19 = 1.363 (4) , N2-C23 = 1.368 (4) , N3-C24 = 1.387 (4) , C4-C19 = 1.448 (4), C23-C24 = 1.445 (4), N4-C42 = 1.138 (4), C42-C43 = 1.449 (4) Å; N1-Ni-N3 = 166.68 (10), N4-Ni-N3 = 96.58 (10), N1-Ni-N4 = 96.73 (10), N2-C23-C24-N3 = 1.53, N1-C4-C19-N2 = 1.43 Further, the molecular structure of the complex was determined by single-crystal X-ray studies (Figure 17). The molecule exhibits a distorted square planar geometry around the nickel center. All the three donating nitrogens of the pincer ligand stay in the same plane and the acetonitrile molecule, which is arranged trans to the o pyridyl nitrogen, lay slightly out of the plane making an angle of about 9 . Similar to the ligand, the two pyrrole substituted aryl rings that are o adjacent to the pyridine ring are twisted about 68 from the NCCNCCN plane in order to reduce the steric interactions. The two aryl rings of the rarer side have also rotated about 18 o 60 from the plane of the metal center due to the steric constraints of the coordinated acetonitrile ligand. The inter pyrrolide angle N1−Ni−N3 is found to be 166.67° and the dihedral angles NCCN involving pyrrolide and pyridyl rings are found to be 1.53° (N1C4C19N2) and 1.43° (N2C23C24N3). This indicates that upon chelation the pyrrole rings are conventionally eclipsed and remain coplanar. The N-Ni bond length of acetonitrile group (Ni-N4 = 1.862(3) Å) is found to be shorter than that of the pyrrole ring (Ni-N1 = 1.896(2) and Ni-N3 = 1.906(2) Å), however the N-Ni bond of the pyridyl nitrogen (Ni-N2 = 1.844(2) Å) is found to be the shortest among the three. Interestingly, the N-Ni bond distance of acetonitrile group observed in the current complex, is found to be significantly shorter as compared with the other nickel-acetonitrile complexes reported earlier (range 2.057 – 2.097 Å).28-36 2.3 Nickel(II) carbonyl complex supported by 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine 2.3.1 Introduction Carbon monoxide is one of the most important and widely used small molecules in organometallic chemistry. Many industrial processes such as catalytic olefin hydroformylation, olefin/CO copolymerization, Monsanto acetic acid process, water-gas shift reactions, and thioester formation in Acetyl coenzyme A synthase etc. have extensive use of numerous carbonylation reactions catalyzed by transition metal catalysts. 55-61 Instead of rare and expensive transition metals such as Rh, Ru and Ir, the use of earth-abundant transition metals have attracted huge attention recently because of their economic advantages. For group 10 elements, scientists are trying to use nickel instead of Pd and Pt for catalytic carbonylation due to lower cost and toxicity. CO insertion chemistry has extensive usage in various multiple-component reactions to form 19 carbonyl containing molecules e.g. acid anhydrides, amides, thiocarbamates, lactones and ketones etc. 55-61 The structure of CO can be explained by the MO description. The lone pairs of carbon and oxygen are diagonal C(2S)-C(2Pz) hybrid. Also, the lone pairs of oxygen are weakly directed than the lone pair of carbon. The low energy antibonding orbitals are able to accept electron density form filled non-bonding metal d orbitals. The condition for the overlapping of the electron density is that the d orbitals have to be of the correct symmetry (Figure 18). 44-47 Figure 18. Orbital overlap in carbon monoxide molecule 71 Orbital overlap results increase in the metal-ligand bond strength and decrease in C-O bond order. This decrease in C-O bond order can be explained by the lowering of IR absorption frequency. One point to note here that only change in π-bond strength and not σ-bond strength corresponds to the vibration observed in the Infrared region. 56-60 Both σ and π bonding are thought to have roles in the bonding between CO and metal. The π-back bonding occurs from the π-d electron delocalization from central metal ion to anti-bonding CO orbital and a strong σ-bond forms by the overlap of σ symmetry orbitals of the metal and CO (Figure 19). This kind of bonding is 20 specially favorable with low valent metals where delocalization of electron density is high into the ligand orbital. Due to the high delocalization of electrons, carbonyl complexes are highly covalent in nature. σ bond π bond Figure 19. Orbital overlap in metal carbonyl bond 72 The first nickel carbonyl, nickel tetracarbonyl was discovered by Mond in 1891. 61 Rapid corrosion of nickel valve was noticed by the workers in the Solvay process for the production of sodium bicarbonate in which ammonia and carbon dioxide vapors were used. This observation directed to the detection of trace amounts of carbon monoxide in the carbon dioxide as well as discovery of nickel tetracarbonyl. 2.3.2 Results & Discussion Considering the history and importance of nickel carbonyl complexes and nice accommodation of acetonitrile in the ligand pocket, synthesis of nickel carbonyl supported by the same ligand was attempted (Figure 20). The ligand 2,6-bis(3,5-ditolyl2-pyrrolyl)pyridine (LH2) was deprotonated by refluxing the ligand with 1.5 equivalent of KH for 1.5 hrs in dry THF under nitrogen atmosphere. Then the excess KH was removed 21 by filtration under nitrogen. The deprotonated potassium salt of the ligand was taken to the next step without isolation. The potassium salt of the ligand in dry THF was stirred with one equivalent of Ni(OTf)2 overnight. Finally THF was removed and the remaining substance was stirred in ether for few minutes. Then the solution was left to settle down. There was a precipitation of insoluble substances. The clear solution was slowly collected with a syringe and passed through a celite bed to completely separate the insoluble part. o Then carbon monoxide gas was passed through the ether solution for 20 minutes at 0 C temperature. The solution saturated with carbon monoxide was left stirring for another 40 minutes. Finally, after filtration through celite bed the volume of the solution was o decreased to one third of its initial volume and kept in the -30 C freezer for few days for crystallization. The bright red crystals diffracted well under X-ray and indicated one CO molecule is attached to the nickel center. The IR spectrum shows a sharp absorption of -1 CO at 2101 cm . The absorption frequency is in the classical region as it is less than the -1 free carbon monoxide (2143 cm ) but well above observed range of other nickel(II) -1 1 13 carbonyl complexes (2030-2070 cm ). The H NMR and C NMR also supported the desired product formation. Interestingly, there was a peak for CO carbon at 174.4 in NMR which sometimes doesn’t show up in metal carbonyls. Figure 20. Synthesis of LNiCO 22 13 C Further, the molecular structure of the complex was determined by single-crystal X-ray studies (Figure 21). The molecule exhibits a distorted square planar geometry around the nickel center. All the three donating nitrogens of the pincer ligand stay in the same plane and the carbon monoxide molecule, which is arranged trans to the o pyridyl nitrogen, lay slightly out of the plane making an angle of about 27 . Figure 21. ORTEP diagram of the molecular structure of complex o Representative bond lengths (Å) and angles ( ). Ni-C22 = 1.808 (3) , Ni-N1 = 1.853 (3) , Ni-N2 = 1.8682 (19) , Ni-N2 = 1.8683 (19), N1-C3 = 1.364 (3) , N2-C7 = 1.372 (3) , N2-C4 = 1.393 (3) , C1-C2 = 1.386 (3) , C4C5 = 1.401 (3), C6-C7 = 1.390 (3), C8-C13 = 1.400 (3), C9-C10 = 1.389 (3) Å; N1-Ni-N2 = 83.19 (6), N1-Ni-C22 = 160.43 (14), Ni-N1-C3 = 117.69 (14), N1-C3-C4-N2 = 2.59 23 Similar to the ligand, the two pyrrole substituted aryl rings that are o adjacent to the pyridine ring are twisted about 44 from the NCCNCCN plane in order to reduce the steric interactions. The two aryl rings of the rear side have also rotated about o 50 from the plane of the metal center due to the steric constraints of the coordinated acetonitrile ligand. The inter pyrrolide angle N1−Ni−N2 is found to be 83.19 °. The molecule is symmetrical. Both the dihedral angles NCCN involving pyrrolide and pyridyl rings are found to be 2.59 ° for (N1C3C4N2). This indicates that upon chelation the pyrrole rings are conventionally eclipsed and remain coplanar. The C22-Ni bond length of CO group (Ni-C22 = 1.808 (3) Å) is found to be shorter than that of the pyrrole ring (Ni-N2 = 1.8682 (19) and Ni-N2 = 1.8683 (19) Å), however the N-Ni bond of the pyridyl nitrogen (Ni-N2 = 1.853 (3) Å) is found to be shorter than that of pyrrole ring and longer than that of carbon monoxide group. Interestingly, the Ni(II)-CO bond distance of 1.808 Å observed in the current complex, is found to be well in the range of observed for other nickel(II) carbonyl complexes (range 1.73 – 1.83 Å). 2.4 Ni(II) ammonia complex supported by 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine 2.4.1 Introduction Activation of small molecules such as N2, H2, O2, CO, NH3 with transition-metal complexes has huge application in synthetic chemistry. Multidentate ligands have shown some important uses in small molecule activation by enhancing the reactivities of the metal center or facilitating ligand-based redox reactions. 62-63 Pincer and pincer-like ligands featuring relatively different conformational flexible frameworks are well known for participating in this kind of reactions. 64-66 In this context, after obtaining CO adduct with Ni(II) supported by the ligand 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine (LH2), 24 focus was shifted to isolate an ammonia adduct with Ni(II) supported by the same ligand. The catalytic ammonia decomposition chemistry has been explored by a large group of scientists recently owing to its many important applications. Ammonia is a potential energy carrier for fuel cells due to its high hydrogen storage capacity and the possibility to produce hydrogen without toxic or greenhouse gases as byproducts. Besides, it is a precursor of aromatic amines that are highly useful and valuable compounds with numerous uses in the pharmaceutical, agrochemical and polymer industries. Huge abundance on earth and extremely low cost made ammonia one of the most useful commodity chemicals. Hartwig and Turculet groups have investigated addition of ammonia to the Iridium pincer complexes. Parvez and coworker activated ammonia with a Ni(II) pincer complex. Leitner group reported rhodium pincer complex catalyzed hydroamination of ethylene with ammonia. Still ammonia activation with pincer complexes is relatively scarce in literature. 62-67 2.4.2 Result & Discussion Based on the above facts, synthesis of the ammonia adduct with Ni(II) supported by the same ligand, 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine (LH2) was attempted (Figure 22). First, the ligand was deprotonated by refluxing the ligand with 1.5 equivalents of KH for 1.5 h in dry THF under nitrogen atmosphere. Then, the excess KH was removed by filtration under nitrogen. The deprotonated potassium salt of the ligand was taken to the next step without isolation. The potassium salt of the ligand in dry THF was stirred with one equivalent of Ni(OTf)2 overnight. Finally, THF was removed and the remaining substance was stirred in ether for few minutes. Then the solution was left to settle down. There was a precipitation of insoluble substances. The clear solution was slowly collected with a syringe and passed through a celite bed to completely separate 25 the insoluble part. Then ammonia gas was passed through the ether solution for 20 o minutes at 0 C temperature. The solution saturated with ammonia was left stirring for another 40 minutes. Finally, after filtration through celite bed the volume of the solution o was decreased to one third of its initial volume and kept in the -30 C freezer for few days for crystallization. The bright red crystals diffracted well under X-ray and indicated one ammonia molecule is attached to the nickel center. The IR spectrum shows sharp -1 1 absorptions of N-H at 3309.6, 3360.2 cm . The H NMR and 13 C NMR also supported the desired product formation. The three NH3 protons give a singlet at 0.49 . Figure 22. Synthesis of LNiNH3 Further, the molecular structure of the complex was determined by single-crystal X-ray studies (Figure 23). The molecule exhibits a distorted square planar geometry around the nickel center. All the three donating nitrogens of the pincer ligand stay in the same plane and the ammonia molecule, which is arranged trans to the pyridyl o nitrogen, lay slightly out of the plane making an angle about 26 . 26 Figure 23. ORTEP diagram of the molecular structure of complex o Representative bond lengths (Å) and angles ( ). Ni-N1 = 1.885 (10) , Ni-N2 = 1.849 (10) , Ni-N3 = 1.887 (10), Ni-N4 = 1.929 (11), N1-C4 = 1.387 (4) , N2-C9 = 1.356 (15) , N2-C5 = 1.355 (15) , N3-C13 = 1.365 (15) , C4C5 = 1.440 (17), C23-C24 = 1.391 (2), C38-C39 = 1.388 (2) Å; N1-Ni-N3 = 163.95 (5), N4-Ni-N3 = 98.60 (5), N1-Ni-N4 = 96.98 (5), N2-C9-C10-N3 = 6.68, N1-C4-C19-N2 = 4.49 Similar to the ligand, the two pyrrole substituted aryl rings that are o adjacent to the pyridine ring are twisted about 41 from the NCCNCCN plane in order to reduce the steric interactions. The two aryl rings of the rarer side have also rotated about o 43 from the plane of the metal center due to the steric constraints of the coordinated ammonia ligand. The inter pyrrolide angle N1−Ni−N3 is found to be 163.95 ° and the dihedral angles NCCN involving pyrrolide and pyridyl rings are found to be 6.68 ° 27 (N1C4C19N2) and 4.49 ° (N2C23C24N3). This indicates that upon chelation the pyrrole rings are conventionally eclipsed and remain coplanar. The N-Ni bond length of ammonia group (Ni-N4 = 1.929(11) Å) is found to be longer than that of the pyrrole ring (Ni-N1 = 1.885(10) and Ni-N3 = 1.887(10) Å). However the N-Ni bond of the pyridyl nitrogen (NiN2 = 1.849(10) Å) is found to be the shortest among the three. 28 Chapter 3 Conclusion In conclusion, a new pyridine-pyrrole based NNN pincer ligand was synthesized and characterized. The ligand synthesis procedure was fast and simple. All intermediate compounds were prepared with good yields and in pure form. The organic precursors were purified with vacuum distillation and dried with molecular sieves. The compound 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine (LH2) was excellent supporting ligand in the preparation of the different nickel(II) adducts. Two Ni(II) pincer complexes supported by the same tridentate, dianionic ligand and nitrogen donors, acetonitrile and ammonia were obtained. Also, it was possible to isolate tetra coordinated nickel(II) carbonyl complex supported by the same ligand. In all these new compounds the ligand 2,6bis(3,5-ditolyl-2-pyrrolyl)pyridine (LH2) is bound to the metal in κ3-fashion through the three nitrogen donor atoms. Single crystals were obtained for all of the compounds and their structures were confirmed by X-ray analysis. The reactivity of the complexes is yet to be studied. However, preliminary results were obtained for the synthesis of nickel(II) hydroxo complex supported by the same ligand and carbon dioxide fixation with the same nickel(II) hydroxo complex. 29 Chapter 4 Experimental Details All experiments were done under purified nitrogen atmosphere with standard schlenk technique or in Glove box. Solvents were bought from various commercial sources and later purified with an Innovative technology SPS-400 PureSolv solvent drying system. Some very hygroscopic solvents were distilled over conventional drying agents and degassed by the freeze-pump-thaw method few times prior to use. All o o glassware were oven dried at 150 C overnight. NMR spectra were recorded at 25 C on 1 JEOL Eclipse 500 and 300 spectrometers ( H: 500.16 MHz or 300.53 MHz; 13 C: 125.77 MHz or 75.57 MHz). Proton and carbon chemical shifts are reported in ppm versus Me4Si. Infrared (IR) spectra were taken on a JASCO FT-IR 410 spectrometer. The mass spectra were acquired on Shimadzu IT-TOF-HRMS. Melting points were obtained on a Mel-Temp II apparatus. All materials were obtained from commercial vendors. 4.1 Synthesis of 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine 1,3-bis(4-tolyl)-2-propen-1-one [chalcone] was prepared following literature known procedure from tolualdehyde and 4-methylacetophenone. Then the chalcone (1.75 g, 7.4 mmol) was reacted with 2,6-pyridinedicarbaldehyde (0.5 g, 3.7 30 mmol), 3-benzyl-5-(-hydroxyethyl)-4-methylthiazolium chloride (0.2 g, 0.74mmol) and sodium t-butoxide (0.57 g, 0.74 mmol) in ethanol at reflux for 24 h to form a brown suspension. Water was added and the mixture was extracted with chloroform. The chloroform was removed to obtain 2,6-bis(2,4-ditolyl-1,4-dioxobutyl)pyridine. The product was washed with hexane to achieve an orange solid. Finally, the intermediate ketone was reacted without further purification with NH4OAc (2.8 g, 37 mmol) in ethanol at reflux for 24 h. Water was added and the yellow solid was filtered and washed with water. Then the o crude product was suspended in 10 mL ethanol and refluxed at 100 C for 7 hrs to obtain 1 a yellow solid of 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine (LH2). (Yield 64%) H NMR (CDCl3, 500.16 MHz, 298 K): 2.38 (s, 12H, CH3) 6.57 (m, 2H), 7.02 (d, J = 8.05, 2H), 7.17-7.22 (m, 9H), 7.38 (d, 4H), 7.47 (d, J = 8 Hz, 4H), 9.56 (2H, NH). 13 1 C{ H} NMR (CDCl3, 125.77 MHz, 298 K): 21.3, 109.7, 117.5, 124.2, 126.6, 127.4, 129.1, 129.8, 133.0, 134.0, 136.3, 136.4, 136.7, 150.3 HRMS-(ESI-) Calculated: 571.29, found: 571.14 M.P. o o compound decomposes to form a black substance at 225 C-230 C. 4.2 Synthesis of LNi(CH3CN) A mixture of the ligand 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine (LH2) (0.1 g, 0.175 mmol) and KH (0.021 g, 0.525 mmol) were taken as solids in a 50 mL Schlenk flask. THF (ca. 10mL) was added to the mixture at room temperature. The reaction 31 mixture was refluxed for 1.5 hrs. Then it was cooled down to room temperature and filtered through a Celite pad (Celite pad was then washed with 5 mL of THF). The filtrate was added to Ni(OTf)2 (0.062 g, 0.175 mmol) in 10 mL of THF and stirred overnight at room temperature. Then THF was removed and the residue was filtered in Ether. Ether was removed under vacuum and 10 mL acetonitrile was added. After 1 h stirring, the solution was filtered and the volume of the solution was decreased to 4 mL. Finally, the acetonitrile solution was diffused slowly with hexane to obtain brown crystals at room temperature. (Yield 34%) H NMR (CDCl3, 500.16 MHz, 298 K): 0.738 (s, 3H, CH3) 2.32 1 (s, 6H, CH3), 2.37 (s, 6H, CH3) 6.06 (s, 2H), 6.60 (d, J = 8 Hz, 2H), 7.04 (t, J = 8 Hz, 1H), 7.15 (m, 8H), 7.36 (d, J = 8 Hz, 4H), 7.62 (d, J = 8.05 Hz, 4H). 13 1 C{ H} NMR (CDCl3, 125.77 MHz, 298 K): 21.2, 110.1, 113.9, 128.0, 129.1, 129.8, 133.9, 134.7, 135.6, 136.0, 136.4, 138.8, 146.2, 154.5 HRMS-(ESI+) Calculated: 666.23, found: 666.21 M.P. o o compound decomposes to form a black substance at 175 C-185 C. 4.3 Synthesis of LNi(CO) A mixture of the ligand 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine (LH2) (0.1 g, 0.175 mmol) and KH (0.021 g, 0.525 mmol) were taken as solids in a 50 mL Schlenk flask. THF (ca. 10 mL) was added to the mixture at room temperature. The reaction mixture was refluxed for 1.5 h. Then it was cooled down to room temperature and filtered 32 through a Celite pad (Celite pad was then washed with 5 mL of THF). The filtrate was added to Ni(OTf)2 (0.062 g, 0.175 mmol) in 10 mL of THF and stirred overnight at room temperature. Then THF was removed and the residue was filtered in Ether. Then anhydrous carbon dioxide gas was passed through the ether solution for 20 minutes at o 0 C. After 1 hour stirring, the solution was filtered and the volume of the solution was o decreased to 4 mL. Red crystals were formed after keeping the solution in the -20 C freeze for 3 days (Yield 24%) H NMR (CDCl3, 500.16 MHz, 298 K): 2.37 (s, 6H, CH3), 1 2.38 (s, 6H, CH3) 6.21 (s, 2H), 6.77 (d, J = 7.45 Hz, 2H), 7.02 (t, J = 8 Hz, 1H), 7.21 (m, 8H), 7.38 (d, J = 7.5 Hz, 4H), 7.47 (d, J = 8.05 Hz, 4H). 13 1 C{ H} NMR (CDCl3, 125.77 MHz, 298 K): 21.3, 112.1, 117.9, 128.9, 129.3, 129.8, 132.9, 134.0, 136.3, 136.5, -1 136.8, 147.3, 150.2, 154.4, 174.4 IR (crystals, ATR, selected band) cm : 2100.9 (CO) HRMS-(ESI+) Calculated: 654.20, found: 654.30 M.P. - compound decomposes to form a o o black substance at 170 C-175 C. 4.4 Synthesis of LNi(NH3) A mixture of the ligand 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine (LH2) (0.1 g, 0.175 mmol) and KH (0.021 g, 0.525 mmol) were taken as solids in a 50 mL Schlenk flask. THF (ca. 10 mL) was added to the mixture at room temperature. The reaction 33 mixture was refluxed for 1.5 h. Then it was cooled down to room temperature and filtered through a Celite pad (Celite pad was then washed with 5 mL of THF). The filtrate was added to Ni(OTf)2 (0.062 g, 0.175 mmol) in 10 mL of THF and stirred overnight at room temperature. Then THF was removed and the residue was filtered in Ether. Then o anhydrous ammonia gas was passed through the ether solution for 20 minutes at 0 C. After 1 hour stirring, the solution was filtered and the volume of the solution was o decreased to 4 mL. Red crystals were formed after keeping the solution in the -20 C freeze for 3 days (Yield 54%) H NMR (CDCl3, 500.16 MHz, 298 K): 0.49 (s, 3H, NH3) 1 2.35 (s, 6H, CH3), 2.38 (s, 6H, CH3) 6.08 (s, 2H), 6.63 (d, J = 8 Hz, 2H), 7.05 (t, J = 8.05 Hz, 1H), 7.19 (m, 8H), 7.36 (d, J = 8.05, 4H), 7.62 (d, J = 7.45 Hz, 4H). 13 1 C{ H} NMR (CDCl3, 125.77 MHz, 298 K): 21.2, 110.1, 113.9, 128.5, 129.1, 129.7, 133.6, 134.0, -1 136.0, 136.4, 136.8, 138.5, 144.8, 154.0 IR (crystals, ATR, selected band) cm : 3309.6, 3360.2 (NH) HRMS-(ESI-) Calculated: 644.22, found: 644.19 M.P. - compound o o decomposes to form a black substance at 125 C-130 C. 34 Appendix A X-ray Data Collection and Selected Bond Distances & Bond Angles 35 X-ray crystallographic data for 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine (LH2) (File name rad77_a) Chemical formula moiety 'C41 H35 N3' Chemical formula weight 569.72 Space group crystal system monoclinic Space group IT number 14 Space group name H-M alt 'P 21/c' Space group name Hall '-P 2ybc' Cell length a 14.9028(11) Cell length b 35.166(3) Cell length c 5.9568(5) Cell angle alpha 90 Cell angle beta 100.9910(19) Cell angle gamma 90 Cell volume 3064.6(4) Cell formula units Z 4 Cell measurement temperature 100(2) Cell measurement reflns used 7739 Cell measurement theta min 3.02 Cell measurement theta max 32.16 Exptl crystal description platy Exptl crystal colour yellow Exptl crystal density diffrn 1.235 Exptl crystal F 000 1208 36 Exptl crystal size max 0.276 Exptl crystal size mid 0.184 Exptl crystal size min 0.118 Diffrn ambient temperature 100(2) Diffrn radiation wavelength 0.71073 Diffrn radiation type MoK\a Diffrn measurement device type 'Bruker D8 Quest' Diffrn measurement method '\f and \w scans' Diffrn reflns number 36061 Diffrn reflns av unetI/netI 0.0709 Diffrn reflns av R equivalents 0.0893 Diffrn reflns limit h min -19 Diffrn reflns limit h max 19 Diffrn reflns limit k min -46 Diffrn reflns limit k max 46 Diffrn reflns limit l min -7 Diffrn reflns limit l max 7 Diffrn reflns theta min 3.016 Diffrn reflns theta max 28.282 Diffrn reflns theta full 25.000 Bond lengths [Å] N1-C1 1.372(3) 37 N1-C4 1.379(3) N1-H1 0.86(3) N2-C19 1.341(3) N2-C23 1.353(3) N3-C27 1.360(3) N3-C24 1.380(3) N3-H3 0.92(3) C1-C2 1.375(4) C1-C5 1.472(3) C2-C3 1.432(3) C2-H2 0.9500 C3-C4 1.387(3) C3-C12 1.478(3) C4-C19 1.470(3) C5-C6 1.384(4) C5-C10 1.401(4) C6-C7 1.393(4) C6-H6 0.9500 C7-C8 1.389(4) C7-H7 0.9500 C8-C9 1.374(4) C8-C11 1.513(3) C9-C10 1.393(4) C9-H9 0.9500 C10-H10 0.9500 38 C11-H11A 0.9800 C11-H11B 0.9800 C11-H11C 0.9800 C12-C13 1.394(3) C12-C17 1.402(3) C13-C14 1.388(3) C13-H13 0.9500 C14-C15 1.393(4) C14-H14 0.9500 C15-C16 1.392(4) C15-C18 1.510(4) C16-C17 1.391(3) C16-H16 0.9500 C17-H17 0.9500 C18-H18A 0.9800 C18-H18B 0.9800 C18-H18C 0.9800 C19-C20 1.402(3) C20-C21 1.387(3) C20-H20 0.9500 C21-C22 1.376(3) C21-H21 0.9500 C22-C23 1.400(3) C22-H22 0.9500 C23-C24 1.458(3) 39 C24-C25 1.393(3) C25-C26 1.417(3) C25-C28 1.492(3) C26-C27 1.390(3) C26-H26 0.9500 C27-C35 1.469(3) C28-C29 1.386(3) C28-C33 1.396(3) C29-C30 1.391(3) C29-H29 0.9500 C30-C31 1.385(4) C30-H30 0.9500 C31-C32 1.392(4) C31-C34 1.509(3) C32-C33 1.398(3) C32-H32 0.9500 C33-H33 0.9500 C34-H34A 0.9800 C34-H34B 0.9800 C34-H34C 0.9800 C35-C36 1.394(3) C35-C40 1.396(3) C36-C37 1.389(3) C36-H36 0.9500 C37-C38 1.398(3) 40 C37-H37 0.9500 C38-C39 1.383(4) C38-C41 1.515(3) C39-C40 1.394(3) C39-H39 0.9500 C40-H40 0.9500 C41-H41A 0.9800 C41-H41B 0.9800 C41-H41C 0.9800 Bond angles [deg] C1-N1-C4 110.9(2) C1-N1-H1 128.7(19) C4-N1-H1 119.8(19) C19-N2-C23 119.41(19) C27-N3-C24 111.57(19) C27-N3-H3 133(2) C24-N3-H3 115(2) N1-C1-C2 106.9(2) N1-C1-C5 120.1(2) C2-C1-C5 132.9(2) C1-C2-C3 108.3(2) 41 C1-C2-H2 125.8 C3-C2-H2 125.8 C4-C3-C2 106.8(2) C4-C3-C12 128.9(2) C2-C3-C12 124.2(2) N1-C4-C3 107.1(2) N1-C4-C19 116.6(2) C3-C4-C19 136.3(2) C6-C5-C10 117.8(2) C6-C5-C1 121.4(2) C10-C5-C1 120.8(2) C5-C6-C7 121.3(3) C5-C6-H6 119.3 C7-C6-H6 119.3 C8-C7-C6 121.0(3) C8-C7-H7 119.5 C6-C7-H7 119.5 C9-C8-C7 117.7(2) C9-C8-C11 121.3(2) C7-C8-C11 121.0(3) C8-C9-C10 122.1(3) C8-C9-H9 118.9 C10-C9-H9 118.9 C9-C10-C5 120.1(3) C9-C10-H10 119.9 42 C5-C10-H10 119.9 C8-C11-H11A 109.5 C8-C11-H11B 109.5 H11A-C11-H11B 109.5 C8-C11-H11C 109.5 H11A-C11-H11C 109.5 H11B-C11-H11C 109.5 C13-C12-C17 117.7(2) C13-C12-C3 121.1(2) C17-C12-C3 121.2(2) C14-C13-C12 121.4(2) C14-C13-H13 119.3 C12-C13-H13 119.3 C13-C14-C15 121.0(2) C13-C14-H14 119.5 C15-C14-H14 119.5 C16-C15-C14 118.0(2) C16-C15-C18 120.6(2) C14-C15-C18 121.4(2) C17-C16-C15 121.3(2) C17-C16-H16 119.3 C15-C16-H16 119.3 C16-C17-C12 120.7(2) C16-C17-H17 119.7 C12-C17-H17 119.7 43 C15-C18-H18A 109.5 C15-C18-H18B 109.5 H18A-C18-H18B 109.5 C15-C18-H18C 109.5 H18A-C18-H18C 109.5 H18B-C18-H18C 109.5 N2-C19-C20 122.2(2) N2-C19-C4 114.48(19) C20-C19-C4 123.3(2) C21-C20-C19 117.7(2) C21-C20-H20 121.1 C19-C20-H20 121.1 C22-C21-C20 120.6(2) C22-C21-H21 119.7 C20-C21-H21 119.7 C21-C22-C23 118.6(2) C21-C22-H22 120.7 C23-C22-H22 120.7 N2-C23-C22 121.4(2) N2-C23-C24 114.24(18) C22-C23-C24 124.4(2) N3-C24-C25 106.2(2) N3-C24-C23 117.7(2) C25-C24-C23 136.1(2) C24-C25-C26 107.59(19) 44 C24-C25-C28 126.2(2) C26-C25-C28 126.1(2) C27-C26-C25 107.9(2) C27-C26-H26 126.0 C25-C26-H26 126.0 N3-C27-C26 106.69(19) N3-C27-C35 121.4(2) C26-C27-C35 131.9(2) C29-C28-C33 118.1(2) C29-C28-C25 121.9(2) C33-C28-C25 120.0(2) C28-C29-C30 121.3(2) C28-C29-H29 119.4 C30-C29-H29 119.4 C31-C30-C29 121.0(2) C31-C30-H30 119.5 C29-C30-H30 119.5 C30-C31-C32 118.2(2) C30-C31-C34 120.5(2) C32-C31-C34 121.4(2) C31-C32-C33 121.0(2) C31-C32-H32 119.5 C33-C32-H32 119.5 C28-C33-C32 120.5(2) C28-C33-H33 119.8 45 C32-C33-H33 119.8 C31-C34-H34A 109.5 C31-C34-H34B 109.5 H34A-C34-H34B 109.5 C31-C34-H34C 109.5 H34A-C34-H34C 109.5 H34B-C34-H34C 109.5 C36-C35-C40 118.1(2) C36-C35-C27 121.0(2) C40-C35-C27 120.9(2) C37-C36-C35 120.8(2) C37-C36-H36 119.6 C35-C36-H36 119.6 C36-C37-C38 121.1(2) C36-C37-H37 119.5 C38-C37-H37 119.5 C39-C38-C37 118.0(2) C39-C38-C41 121.4(2) C37-C38-C41 120.6(2) C38-C39-C40 121.3(2) C38-C39-H39 119.3 C40-C39-H39 119.3 C39-C40-C35 120.7(2) C39-C40-H40 119.7 C35-C40-H40 119.7 46 C38-C41-H41A 109.5 C38-C41-H41B 109.5 H41A-C41-H41B 109.5 C38-C41-H41C 109.5 H41A-C41-H41C 109.5 H41B-C41-H41C 109.5 X-ray crystallographic data for LNi(CH3CN) (File name - dias960_0m_a) Chemical formula moiety 'C49H50N4Ni' Chemical formula weight 753.64 Space group crystal system Triclinic Space group name H-M alt 'P-1' Cell length a 11.2735(16) Cell length b 14.1808(19) Cell length c 14.688(5) Cell angle alpha 67.162(2) Cell angle beta 68.881(2) Cell angle gamma 80.665(2) Cell volume 2018.0(5) Cell formula units Z 2 47 Cell measurement temperature 100(2) Cell measurement reflns used 8799 Cell measurement theta min 2.45 Cell measurement theta max 32.84 Exptl crystal description prism Exptl crystal colour colorless Exptl crystal density diffrn 1.240 Exptl crystal F 000 800 Exptl crystal size max 0.20 Exptl crystal size mid 0.12 Exptl crystal size min 0.09 Diffrn ambient temperature 100(2) Diffrn radiation wavelength 0.71073 Diffrn radiation type MoK\a Diffrn measurement device type 'Bruker APEX-II CCD' Diffrn measurement method '\f and \w scans' Diffrn reflns number 18916 Diffrn reflns av unetI/netI 0.0746 Diffrn reflns av R equivalents 0.0557 Diffrn reflns limit h min -14 Diffrn reflns limit h max 14 Diffrn reflns limit k min -17 Diffrn reflns limit k max 17 Diffrn reflns limit l min -18 48 Diffrn reflns limit l max 18 Diffrn reflns theta min 2.07 Diffrn reflns theta max 26.37 Bond lengths [Å] Ni-N2 1.844(2) Ni-N4 1.862(3) Ni-N1 1.896(2) Ni-N3 1.906(2) N1-C1 1.373(4) N1-C4 1.398(4) N2-C19 1.363(4) N2-C23 1.368(4) N3-C27 1.379(4) N3-C24 1.387(4) N4-C42 1.138(4) C1-C2 1.402(4) C1-C5 1.472(4) C2-C3 1.405(4) C2-H2 0.9500 C3-C4 1.400(4) C3-C12 1.488(4) 49 C4-C19 1.448(4) C5-C10 1.389(4) C5-C6 1.395(4) C6-C7 1.384(4) C6-H6 0.9500 C7-C8 1.395(5) C7H7 0.9500 C8-C9 1.388(5) C8-C11 1.510(5) C9-C10 1.390(4) C9-H9 0.9500 C10-H10 0.9500 C11-H11A 0.9800 C11-H11B 0.9800 C11-H11C 0.9800 C12-C13 1.394(4) C12-C17 1.395(4) C13-C14 1.378(5) C13-H13 0.9500 C14-C15 1.391(5) C14-H14 0.9500 C15-C16 1.395(5) C15-C18 1.508(4) C16-C17 1.391(4) C16-H16 0.9500 50 C17-H17 0.9500 C18-H18A 0.9800 C18-H18B 0.9800 C18-H18C 0.9800 C19-C20 1.388(4) C20-C21 1.379(4) C20-H20 0.9500 C21-C22 1.387(4) C21-H21 0.9500 C22-C23 1.387(4) C22-H22 0.9500 C23-C24 1.445(4) C24-C25 1.398(4) C25-C26 1.397(4) C25-C28 1.482(4) C26-C27 1.400(4) C26-H26 0.9500 C27-C35 1.477(4) C28-C29 1.389(4) C28-C33 1.389(4) C29-C30 1.387(4) C29-H29 0.9500 C30-C31 1.394(5) C30-H30 0.9500 C31-C32 1.386(5) 51 C31-C34 1.514(4) C32-C33 1.389(5) C32-H32 0.9500 C33-H33 0.9500 C34-H34A 0.9800 C34-H34B 0.9800 C34-H34C 0.9800 C35-C40 1.387(5) C35-C36 1.401(5) C36-C37 1.383(5) C36-H36 0.9500 C37-C38 1.382(6) C37-H37 0.9500 C38-C39 1.394(6) C38-C41 1.513(5) C39-C40 1.393(5) C39-H39 0.9500 C40-H40 0.9500 C41-H41A 0.9800 C41-H41B 0.9800 C41-H41C 0.9800 C42-C43 1.449(4) C43-H43A 0.9800 C43-H43B 0.9800 C43-H43C 0.9800 52 C44-C45 1.567(9) C44-H44A 0.9800 C44-H44B 0.9800 C44-H44C 0.9800 C45-C46 1.336(11) C45-H45A 0.9900 C45-H45B 0.9900 C46-C47 1.517(11) C46-H46A 0.9900 C46-H46B 0.9900 C47-C48 1.409(9) C47-H47A 0.9900 C47-H47B 0.9900 C48-C49 1.476(9) C48-H48A 0.9900 C48-H48B 0.9900 C49-H49A 0.9800 C49-H49B 0.9800 C49-H49C 0.9800 Bond angles [deg] N2-Ni-N4 167.99(11) 53 N2-Ni-N1 83.38(10) N4-Ni-N1 96.73(10) N2-Ni-N3 83.53(10) N4-Ni-N3 96.58(10) N1-Ni-N3 166.68(10) C1-N1-C4 106.5(2) C1-N1-Ni 138.4(2) C4-N1-Ni 113.41(18) C19-N2-C23 122.2(3) C19-N2-Ni 118.6(2) C23-N2-Ni 118.0(2) C27-N3-C24 106.2(2) C27-N3-Ni 138.7(2) C24-N3-Ni 112.50(19) C42-N4-Ni 176.8(3) N1-C1-C2 109.6(3) N1-C1-C5 124.9(3) C2-C1-C5 125.4(3) C1-C2-C3 107.9(3) C1-C2-H2 126.1 C3-C2-H2 126.1 C4-C3-C2 105.9(3) C4-C3-C12 128.3(3) C2-C3-C12 125.8(3) N1-C4-C3 110.2(3) 54 N1-C4-C19 113.8(2) C3-C4-C19 135.0(3) C10-C5-C6 118.1(3) C10-C5-C1 119.9(3) C6-C5-C1 122.0(3) C7-C6-C5 120.7(3) C7-C6-H6 119.6 C5-C6-H6 119.6 C6-C7-C8 121.1(3) C6-C7-H7 119.5 C8-C7-H7 119.5 C9-C8-C7 118.2(3) C9-C8-C11 120.8(3) C7-C8-C11 121.1(3) C8-C9-C10 120.8(3) C8-C9-H9 119.6 C10-C9-H9 119.6 C5-C10-C9 121.1(3) C5-C10-H10 119.4 C9-C10-H10 119.4 C8-C11-H11A 109.5 C8-C11-H11B 109.5 H11A-C11-H11B 109.5 C8-C11-H11C 109.5 H11A-C11-H11C 109.5 55 H11B-C11-H11C 109.5 C13-C12-C17 117.9(3) C13-C12-C3 120.8(3) C17-C12-C3 121.3(3) C14-C13-C12 121.1(3) C14-C13-H13 119.5 C12-C13-H13 119.5 C13-C14-C15 121.6(3) C13-C14-H14 119.2 C15-C14-H14 119.2 C14-C15-C16 117.4(3) C14-C15-C18 121.6(3) C16-C15-C18 120.9(3) C17-C16-C15 121.2(3) C17-C16-H16 119.4 C15-C16-H16 119.4 C16-C17-C12 120.7(3) C16-C17-H17 119.7 C12-C17-H17 119.7 C15-C18-H18A 109.5 C15-C18-H18B 109.5 H18A-C18-H18B 109.5 C15-C18-H18C 109.5 H18A-C18-H18C 109.5 H18B-C18-H18C 109.5 56 N2-C19-C20 119.2(3) N2-C19-C4 110.4(3) C20-C19-C4 130.2(3) C21-C20-C19 119.1(3) C21-C20-H20 120.5 C19-C20-H20 20.5 C20-C21-C22 121.5(3) C20-C21-H21 119.3 C22-C21-H21 119.3 C23-C22-C21 118.5(3) C23-C22-H22 120.7 C21-C22-H22 120.7 N2-C23-C22 119.5(3) N2-C23-C24 110.3(3) C22-C23-C24 130.1(3) N3-C24-C25 110.6(3) N3-C24-C23 114.7(2) C25-C24-C23 134.0(3) C26-C25-C24 105.7(3) C26-C25-C28 127.0(3) C24-C25-C28 127.2(3) C25-C26-C27 108.1(3) C25-C26-H26 125.9 C27-C26-H26 125.9 N3-C27-C26 109.3(3) 57 N3-C27-C35 124.6(3) C26-C27-C35 125.6(3) C29-C28-C33 117.9(3) C29-C28-C25 121.1(3) C33-C28-C25 121.0(3) C30-C29-C28 121.5(3) C30-C29-H29 119.3 C28-C29-H29 119.3 C29-C30-C31 120.7(3) C29-C30-H30 119.6 C31-C30-H30 119.6 C32-C31-C30 117.5(3) C32-C31-C34 122.1(3) C30-C31-C34 120.4(3) C31-C32-C33 121.9(3) C31-C32-H32 119.1 C33-C32-H32 119.1 C28-C33-C32 120.4(3) C28-C33-H33 119.8 C32-C33-H33 119.8 C31-C34-H34A 109.5 C31-C34-H34B 109.5 H34A-C34-H34B 109.5 C31-C34-H34C 109.5 H34A-C34-H34C 109.5 58 H34B-C34-H34C 109.5 C40-C35-C36 118.4(3) C40-C35-C27 122.3(3) C36-C35-C27 119.1(3) C37-C36-C35 120.8(4) C37-C36-H36 119.6 C35-C36-H36 119.6 C38-C37-C36 120.9(4) C38-C37-H37 119.6 C36-C37-H37 119.6 C37-C38-C39 118.7(3) C37-C38-C41 120.5(4) C39-C38-C41 120.8(4) C40-C39-C38 120.6(4) C40-C39-H39 119.7 C38-C39-H39 119.7 C35-C40-C39 120.5(3) C35-C40-H40 119.7 C39-C40-H40 119.7 C38-C41-H41A 109.5 C38-C41-H41B 109.5 H41A-C41-H41B 109.5 C38-C41-H41C 109.5 H41A-C41-H41C 109.5 H41B-C41-H41C 109.5 59 N4-C42-C43 177.0(3) C42-C43-H43A 109.5 C42-C43-H43B 109.5 H43A-C43-H43B 109.5 C42-C43-H43C 109.5 H43A-C43-H43C 109.5 H43B-C43-H43C 109.5 C45-C44-H44A 109.5 C45-C44-H44B 109.5 H44A-C44-H44B 109.5 C45-C44-H44C 109.5 H44A-C44-H44C 109.5 H44B-C44-H44C 109.5 C46-C45-C44 116.6(9) C46-C45-H45A 108.1 C44-C45-H45A 108.1 C46-C45-H45B 108.1 C44-C45-H45B 108.1 H45A-C45-H45B 107.3 C45-C46-C47 120.8(10) C45-C46-H46A 107.1 C47-C46-H46A 107.1 C45-C46-H46B 107.1 C47-C46-H46B 107.1 H46A-C46-H46B 106.8 60 C48-C47-C46 116.6(10) C48-C47-H47A 108.1 C46-C47-H47A 108.1 C48-C47-H47B 108.1 C46-C47-H47B 108.1 H47A-C47-H47B 107.3 C47-C48-C49 111.3(7) C47-C48-H48A 109.4 C49-C48-H48A 109.4 C47-C48-H48B 109.4 C49-C48-H48B 109.4 H48A-C48-H48B 108.0 C48-C49-H49A 109.5 C48-C49-H49B 109.5 H49A-C49-H49B 109.5 C48-C49-H49C 109.5 H49A-C49-H49C 109.5 H49B-C49-H49C 109.5 61 X-ray crystallographic data for LNiCO (File name - rad76_0m_a) Chemical formula moiety 'C42 H33 N3NiO' Chemical formula weight 654.42 Space group crystal system monoclinic Space group IT number 14 Space group name H-M alt 'P 21/c' Space group name Hall '-P 2ybc' Cell length a 6.6482(4) Cell length b 27.1709(18) Cell length c 9.1322(6) Cell angle alpha 90 Cell angle beta 101.0700(12) Cell angle gamma 90 Cell volume 1618.92(18) Cell formula units Z 2 Cell measurement temperature 100(2) Cell measurement reflns used 5886 Cell measurement theta min 3.00 Cell measurement theta max 30.47 Exptl crystal description platy Exptl crystal colour yellow Exptl crystal density diffrn 1.342 62 Exptl crystal F 000 684 Exptl crystal size max 0.363 Exptl crystal size mid 0.265 Exptl crystal size min 0.048 Diffrn ambient temperature 100(2) Diffrn radiation wavelength 0.71073 Diffrn radiation type MoK\a Diffrn measurement device type 'Bruker D8 Quest' Diffrn measurement method '\f and \w scans' Diffrn reflns number 17505 Diffrn reflns av unetI/netI 0.0429 Diffrn reflns av R equivalents 0.0534 Diffrn reflns limit h min -8 Diffrn reflns limit h max 8 Diffrn reflns limit k min -35 Diffrn reflns limit k max 35 Diffrn reflns limit l min -11 Diffrn reflns limit l max 11 Diffrn reflns theta min 2.999 Diffrn reflns theta max 27.485 Diffrn reflns theta full 25.000 Bond lengths [Å] 63 Ni-C22 1.808(3) Ni-N1 1.853(3) Ni-N2 1.8682(19) Ni-N2 1.8683(19) O1-C22 1.129(4) N1-C3 1.364(3) N1-C3 1.364(3) N2-C7 1.372(3) N2-C4 1.393(3) C1-C2 1.386(3) C1-C2 1.386(3) C1-H1 0.9500 C2-C3 1.402(3) C2-H2 0.9500 C3-C4 1.443(3) C4-C5 1.401(3) C5-C6 1.411(3) C5-C8 1.483(3) C6-C7 1.390(3) C6-H6 0.9500 C7-C15 1.478(3) C8-C9 1.395(3) C8-C13 1.400(3) C9-C10 1.389(3) 64 C9-H9 0.9500 C10-C11 1.385(4) C10-H10 0.9500 C11-C12 1.403(4) C11-C14 1.515(3) C12-C13 1.391(3) C12-H12 0.9500 C13-H13 0.9500 C14-H14A 0.9800 C14-H14B 0.9800 C14-H14C 0.9800 C15-C20 1.396(3) C15-C16 1.401(3) C16-C17 1.390(3) C16-H16 0.9500 C17-C18 1.392(4) C17-H17 0.9500 C18-C19 1.392(4) C18-C21 1.512(4) C19-C20 1.391(3) C19-H19 0.9500 C20-H20 0.9500 C21-H21A 0.9800 C21-H21B 0.9800 C21-H21C 0.9800 65 Bond angles [deg] C22-Ni-N1 160.43(14) C22-Ni-N2 97.39(6) N1-Ni-N2 83.19(6) C22-Ni-N2 97.39(6) N1-Ni-N2 83.19(6) N2-Ni-N2 165.20(12) C3-N1-C3 124.2(3) C3-N1-Ni 117.69(14) C3-N1-Ni 117.69(14) C7-N2-C4 107.30(19) C7-N2-Ni 137.40(16) C4-N2-Ni 114.65(16) C2-C1-C2 122.1(3) C2-C1-H1 118.9 C2-C1-H1 118.9 C1-C2-C3 118.6(2) C1-C2-H2 120.7 C3-C2-H2 120.7 N1-C3-C2 118.2(2) N1-C3-C4 110.9(2) C2-C3-C4 130.9(2) 66 N2-C4-C5 109.6(2) N2-C4-C3 112.8(2) C5-C4-C3 137.5(2) C4-C5-C6 105.6(2) C4-C5-C8 129.0(2) C6-C5-C8 125.4(2) C7-C6-C5 108.4(2) C7-C6-H6 125.8 C5-C6-H6 125.8 N2-C7-C6 109.1(2) N2-C7-C15 122.4(2) C6-C7-C15 128.5(2) C9-C8-C13 117.6(2) C9-C8-C5 122.2(2) C13-C8-C5 120.2(2) C10-C9-C8 121.0(2) C10-C9-H9 119.5 C8-C9-H9 119.5 C11-C10-C9 121.6(2) C11-C10-H10 119.2 C9-C10-H10 119.2 C10-C11-C12 117.8(2) C10-C11-C14 122.4(2) C12-C11-C14 119.8(2) C13-C12-C11 120.7(2) 67 C13-C12-H12 119.6 C11-C12-H12 119.6 C12-C13-C8 121.2(2) C12-C13-H13 119.4 C8-C13-H13 119.4 C11-C14-H14A 109.5 C11-C14-H14B 109.5 H14A-C14-H14B 109.5 C11-C14-H14C 109.5 H14A-C14-H14C 109.5 H14B-C14-H14C 109.5 C20-C15-C16 118.0(2) C20-C15-C7 121.5(2) C16-C15-C7 120.5(2) C17-C16-C15 120.7(2) C17-C16-H16 119.7 C15-C16-H16 119.7 C16-C17-C18 121.3(2) C16-C17-H17 119.3 C18-C17-H17 119.3 C17-C18-C19 118.0(2) C17-C18-C21 121.5(2) C19-C18-C21 120.5(2) C20-C19-C18 121.2(2) C20-C19-H19 119.4 68 C18-C19-H19 119.4 C19-C20-C15 120.9(2) C19-C20-H20 119.6 C15-C20-H20 119.6 C18-C21-H21A 109.5 C18-C21-H21B 109.5 H21A-C21-H21B 109.5 C18-C21-H21C 109.5 H21A-C21-H21C 109.5 H21B-C21-H21C 109.5 O1-C22-Ni 166.0(3) X-ray crystallographic data for LNiNH3 (File name - rad71_a) Chemical formula moiety 'C41 H36 N4Ni' Chemical formula weight 643.45 Space group crystal system monoclinic Space group IT number 14 Space group name H-M alt 'P 21/c' Space group name Hall '-P 2ybc' Cell length a 15.9773(6) Cell length b 14.9441(5) 69 Cell length c 14.3238(5) Cell angle alpha 90 Cell angle beta 107.8140(8) Cell angle gamma 90 Cell volume 3256.1(2) Cell formula units Z 4 Cell measurement temperature 100(2) Cell measurement reflns used 9841 Cell measurement theta min 2.99 Cell measurement theta max 39.36 Exptl crystal description platy Exptl crystal colour red Exptl crystal density diffrn 1.313 Exptl crystal F 000 1352 Exptl crystal size max 0.459 Exptl crystal size mid 0.409 Exptl crystal size min 0.140 Diffrn ambient temperature 100(2) Diffrn radiation wavelength 0.71073 Diffrn radiation type MoK\a Diffrn measurement device type 'Bruker D8 Quest' Diffrn measurement method '\f and \w scans' Diffrn reflns number 48278 Diffrn reflns av unetI/netI 0.0200 Diffrn reflns av R equivalents 0.0260 70 Diffrn reflns limit h min -22 Diffrn reflns limit h max 22 Diffrn reflns limit k min -35 Diffrn reflns limit k max 35 Diffrn reflns limit l min -21 Diffrn reflns limit l max 21 Diffrn reflns theta min 2.876 Diffrn reflns theta max 30.508 Diffrn reflns theta full 25.000 Bond lengths [Å] Ni-N2 1.8490(10) Ni-N1 1.8857(10) Ni-N3 1.8877(10) Ni-N4 1.9293(11) N1-C1 1.3679(16) N1-C4 1.3870(15) N2-C5 1.3553(15) N2-C9 1.3557(15) N3-C13 1.3654(15) N3-C10 1.3920(15) N4-H1N4 0.89(3) N4-H2N4 0.85(3) 71 N4-H3N4 0.86(3) C1-C2 1.3993(17) C1-C14 1.4698(17) C2-C3 1.4085(18) C2-H2 0.9500 C3-C4 1.3968(17) C3-C21 1.4816(17) C4-C5 1.4400(17) C5-C6 1.3988(16) C6-C7 1.3891(18) C6-H6 0.9500 C7-C8 1.3931(17) C7-H7 0.9500 C8-C9 1.3957(17) C8-H8 0.9500 C9-C10 1.4512(16) C10-C11 1.4040(16) C11-C12 1.4150(17) C11-C35 1.4732(17) C12-C13 1.3994(17) C12-H12 0.9500 C13-C28 1.4702(17) C14-C19 1.3975(19) C14-C15 1.4021(19) C15-C16 1.3906(18) 72 C15-H15 0.9500 C16-C17 1.392(2) C16-H16 0.9500 C17-C18 1.391(2) C17-C20 1.509(2) C18-C19 1.3927(19) C18-H18 0.9500 C19-H19 0.9500 C20-H20A 0.9800 C20-H20B 0.9800 C20-H20C 0.9800 C21-C22 1.3916(19) C21-C26 1.3936(19) C22-C23 1.3938(19) C22-H22 0.9500 C23-C24 1.391(2) C23-H23 0.9500 C24-C25 1.3873(19) C24-C27 1.5027(19) C25-C26 1.3922(18) C25-H25 0.9500 C26-H26 0.9500 C27-H27A 0.9800 C27-H27B 0.9800 C27-H27C 0.9800 73 C28-C33 1.3984(18) C28-C29 1.3980(17) C29-C30 1.3893(19) C29-H29 0.9500 C30-C31 1.389(2) C30-H30 0.9500 C31-C32 1.396(2) C31-C34 1.5037(19) C32-C33 1.3917(18) C32-H32 0.9500 C33-H33 0.9500 C34-H34A 0.9800 C34-H34B 0.9800 C34-H34C 0.9800 C35-C36 1.3976(18) C35-C40 1.3992(17) C36-C37 1.3912(18) C36-H36 0.9500 C37-C38 1.3961(19) C37-H37 0.9500 C38-C39 1.388(2) C38-C41 1.508(2) C39-C40 1.3945(19) C39-H39 0.9500 C40-H40 0.9500 74 C41-H41A 0.9800 C41-H41B 0.9800 C41-H41C 0.9800 Bond angles [deg] N2-Ni-N1 83.41(4) N2-Ni-N3 82.95(4) N1-Ni-N3 163.95(5) N2-Ni-N4 162.16(5) N1-Ni-N4 96.98(5) N3-Ni-N4 98.60(5) C1-N1-C4 106.74(10) C1-N1-Ni 140.11(9) C4-N1-Ni 113.07(8) C5-N2-C9 123.28(11) C5-N2-Ni 117.39(8) C9-N2-Ni 118.43(8) C13-N3-C10 107.19(10) C13-N3-Ni 138.51(9) C10-N3-Ni 114.30(8) Ni-N4-H1N4 112.8(16) 75 Ni-N4-H2N4 120.5(18) H1N4-N4-H2N4 103(2) Ni-N4-H3N4 106.2(15) H1N4-N4-H3N4 112(2) H2N4-N4-H3N4 102(2) N1-C1-C2 109.45(11) N1-C1-C14 123.63(11) C2-C1-C14 126.53(11) C1-C2-C3 107.83(11) C1-C2-H2 126.1 C3-C2-H2 126.1 C4-C3-C2 105.53(11) C4-C3-C21 126.96(11) C2-C3-C21 127.49(11) N1-C4-C3 110.44(11) N1-C4-C5 113.97(10) C3-C4-C5 135.44(11) N2-C5-C6 119.42(11) N2-C5-C4 110.79(10) C6-C5-C4 129.79(11) C7-C6-C5 118.22(11) C7-C6-H6 120.9 C5-C6-H6 120.9 C6-C7-C8 121.36(12) C6-C7-H7 119.3 76 C8-C7-H7 119.3 C7-C8-C9 118.75(11) C7-C8-H8 120.6 C9-C8-H8 120.6 N2-C9-C8 118.92(11) N2-C9-C10 110.49(10) C8-C9-C10 130.58(11) N3-C10-C11 109.98(10) N3-C10-C9 113.08(10) C11-C10-C9 136.94(11) C10-C11-C12 105.46(11) C10-C11-C35 130.14(11) C12-C11-C35 124.37(11) C13-C12-C11 107.90(11) C13-C12-H12 126.1 C11-C12-H12 126.1 N3-C13-C12 109.46(11) N3-C13-C28 123.82(11) C12-C13-C28 126.61(11) C19-C14-C15 117.93(12) C19-C14-C1 120.81(12) C15-C14-C1 121.12(12) C16-C15-C14 120.75(13) C16-C15-H15 119.6 C14-C15-H15 119.6 77 C15-C16-C17 121.14(14) C15-C16-H16 119.4 C17-C16-H16 119.4 C18-C17-C16 118.21(13) C18-C17-C20 121.27(15) C16-C17-C20 120.48(15) C17-C18-C19 121.08(13) C17-C18-H18 119.5 C19-C18-H18 119.5 C18-C19-C14 120.87(13) C18-C19-H19 119.6 C14-C19-H19 119.6 C17-C20-H20A 109.5 C17-C20-H20B 109.5 H20A-C20-H20B 109.5 C17-C20-H20C 109.5 H20A-C20-H20C 109.5 H20B-C20-H20C 109.5 C22-C21-C26 117.84(12) C22-C21-C3 120.99(12) C26-C21-C3 121.17(12) C21-C22-C23 120.87(13) C21-C22-H22 119.6 C23-C22-H22 119.6 C24-C23-C22 121.30(13) 78 C24-C23-H23 119.4 C22-C23-H23 119.4 C25-C24-C23 117.63(12) C25-C24-C27 121.09(13) C23-C24-C27 121.28(13) C24-C25-C26 121.38(13) C24-C25-H25 119.3 C26-C25-H25 119.3 C25-C26-C21 120.92(12) C25-C26-H26 119.5 C21-C26-H26 119.5 C24-C27-H27A 109.5 C24-C27-H27B 109.5 H27A-C27-H27B 109.5 C24-C27-H27C 109.5 H27A-C27-H27C 109.5 H27B-C27-H27C 109.5 C33-C28-C29 118.32(12) C33-C28-C13 121.78(11) C29-C28-C13 119.81(12) C30-C29-C28 120.61(13) C30-C29-H29 119.7 C28-C29-H29 119.7 C29-C30-C31 121.15(13) C29-C30-H30 119.4 79 C31-C30-H30 119.4 C30-C31-C32 118.43(12) C30-C31-C34 120.21(14) C32-C31-C34 121.36(15) C33-C32-C31 120.77(13) C33-C32-H32 119.6 C31-C32-H32 119.6 C32-C33-C28 120.69(12) C32-C33-H33 119.7 C28-C33-H33 119.7 C31-C34-H34A 109.5 C31-C34-H34B 109.5 H34A-C34-H34B 109.5 C31-C34-H34C 109.5 H34A-C34-H34C 109.5 H34B-C34-H34C 109.5 C36-C35-C40 117.73(12) C36-C35-C11 121.83(11) C40-C35-C11 120.39(12) C37-C36-C35 121.15(12) C37-C36-H36 119.4 C35-C36-H36 119.4 C36-C37-C38 121.06(13) C36-C37-H37 119.5 C38-C37-H37 119.5 80 C39-C38-C37 117.85(13) C39-C38-C41 121.65(14) C37-C38-C41 120.50(14) C38-C39-C40 121.50(13) C38-C39-H39 119.3 C40-C39-H39 119.3 C39-C40-C35 120.72(13) C39-C40-H40 119.6 C35-C40-H40 119.6 C38-C41-H41A 109.5 C38-C41-H41B 109.5 H41A-C41-H41B 109.5 C38-C41-H41C 109.5 H41A-C41-H41C 109.5 H41B-C41-H41C 109.5 81 Appendix B Selected Spectroscopy Data 82 1 Figure 24. H NMR spectrum of 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine (LH2) 83 Figure 25. 13 C NMR spectrum of 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine (LH2) 84 1 Figure 26. H NMR spectrum of LNi(CH3CN) 85 Figure 27. 13 C NMR spectrum of LNi(CH3CN) 86 Figure 28. Infrared spectrum of LNiCO 87 Figure 29. Infrared spectrum of LNiNH3 88 Table 1. Summary of NMR data of LH2, LNiCH3CN, LNiCO, LNiNH3 1 H = 2.38 (s, 12H, CH3) 6.57 (m, 2H, pyrrole), 7.02 (d, J = 8.05, 2H), 7.17-7.22 (m, 9H), 7.38 (d, 4H), 7.47 (d, J = 8 Hz, 4H), 9.56 (2H, NH). 1 H = 0.738 (s, 3H, CH3CN) 2.32 (s, 6H, CH3), 2.37 (s, 6H, CH3) 6.06 (s, 2H, pyrrole), 6.60 (d, J = 8 Hz, 2H), 7.04 (t, J = 8 Hz, 1H), 7.15 (m, 8H), 7.36 (d, J = 8 Hz, 4H), 7.62 (d, J = 8.05 Hz, 4H). 1 H = 2.37 (s, 6H, CH3), 2.38 (s, 6H, CH3) 6.21 (s, 2H,pyrrole), 6.77 (d, J = 7.45 Hz, 2H), 7.02 (t, J = 8 Hz, 1H), 7.21 (m, 8H), 7.38 (d, J = 7.5 Hz, 4H), 7.47 (d, J = 8.05 Hz, 4H). 1 13 13 13 13 1 C{ H} = 21.3 (CH3), 109.7 (CH pyrrole), 117.5, 124.2, 126.6, 127.4, 129.1, 129.8, 133.0, 134.0, 136.3, 136.4, 136.7, 150.3 (o-C pyridine) 1 C{ H} = 21.2 (CH3), 110.1 (CH pyrrole), 113.9, 128.0, 129.1, 129.8, 133.9, 134.7, 135.6, 136.0, 136.4, 138.8, 146.2, 154.5 (o-C pyridine) 1 C{ H} = 21.3 (CH3), 112.1 (CH pyrrole), 117.9, 128.9, 129.3, 129.8, 132.9, 134.0, 136.3, 136.5, 136.8, 147.3, 150.2, 154.4(o-C pyridine), 174.4 (CO) 89 H = 0.49 (s, 3H, NH3) 2.35 (s, 6H, CH3), 2.38 (s, 6H, CH3) 6.08 (s, 2H,pyrrole), 6.63 (d, J = 8 Hz, 2H), 7.05 (t, J = 8.05 Hz, 1H), 7.19 (m, 8H), 7.36 (d, J = 8.05, 4H), 7.62 (d, J = 7.45 Hz, 4H). 1 C{ H} = 21.2 (CH3), 110.1 (CH pyrrole), 113.9, 128.5, 129.1, 129.7, 133.6, 134.0, 136.0, 136.4, 136.8, 138.5, 144.8, 154.0 (o-C pyridine) References 1. Pincer Ligands with Strong σ-Donors at the Central Position – PhD Thesis, Javier Borau-Garcia, University of Calgary, Canada 2. A Well-Defined Ni Pincer Catalyst for Cross Coupling of Non-Activated Alkyl Halides and Direct C-H Alkylation – PhD Thesis, Oleg Vechorkin, Ecole Polytechnic 3. Preparation of Ruthenium and Iridium Pincer-Type Pyridylidenes – MS Thesis, Aristidis Pantelis Telly Athanasopoulos, University of Waterloo, Canada 4. Albrecht, M.; van Koten, G. Angew. Chem. Int. Ed. 2001, 40, 3750 5. Moulton, C. J.; Shaw, B. L. J. Chem. Soc., Dalton Trans. 1976, 1020 6. Crocker, C.; Empsall, H. D.; Errington, R. J.; Hyde, E. M.; Mcdonald, W. S.; Markham, R.; Norton, M. C.; Shaw, B. L.; Weeks, B. J. Chem. Soc., Dalton Trans. 1982, 1217 7. Crocker, C.; Errington, R. J.; McDonald, W. S.; Odell, K. J.; Shaw, B. L.; Goodfellow, R. J. J. Chem. Soc., Chem. Comm. 1979, 498. 8. Briggs, J. R.; Constable, A. G.; Mcdonald, W. S.; Shaw, B. L. J. Chem. Soc., Dalton Trans. 1982, 1225 9. Errington, R. J.; Shaw, B. L. J. Organomet. Chem. 1982, 238, 319 10. Morales-Morales, D.; Jensen, C. M. The Chemistry of Pincer Compounds; 1st ed.; Elsevier: Amsterdam ; Boston, 2007. 11. Morales-Morales, D.; Jensen, C. M. The Chemistry of Pincer Compounds; 1 ed.; Oxford Elsevier: Amsterdam, 2007. 90 st 12. Chirik, P. J.; Wieghardt, K. Science, 2010, 327-794. 13. Fryzuk, M. D.; Montgomery, C. D. Coord. Chem. Rev., 1989, 95, 1. 14. Hawk, J. L.; Craig, S. L. Top. Organomet. Chem. 2013, 40, 319. 15. Limberg, C. Angew. Chem., Int. Ed. 2009, 48, 2270. 16. Lyaskovskyy, V.; de Bruin, B. ACS Catal. 2012, 2, 270. 17. Slagt, M. Q.; van Zwieten, D. A. P.; Moerkerk, A. J. C. M.;Gebbink, R. J. M. K.; van Koten, G. Coord. Chem. Rev. 2004, 248, 2275. 18. Milko, E.; Milstein, D. Chem. Rev. 2003, 103, 1759. 19. Van Koten, G. J. Organomet. Chem. 2013, 730, 156. 20. Vigalok, A.; Milstein, D. Acc. Chem. Res. 2001, 34, 798. 21. Flores, J. A.; Andino, J. G.; Tsvetkov, N. P.; Pink, M.; Wolfe, R. J.; Head, A. R.; Lichtenberger, D. L.; Massa, J. P.; Caulton, K. G. Inorg. Chem. 2011, 50, 8121. 22. Flores, J. A.; Komine, N.; Pal, K.; Pinter, B.; Pink, M.; Chen, C.H.; Caulton, K. G.; Mindiola, D. J. ACS Catal. 2012, 2, 2066. 23. Searles, K.; Pink, M.; Caulton, K. G.; Mindiola, D. J. Dalton Trans. 2012, 41, 9619 24. Liu, Q.; Thorne, L.; Kozin, I.; Song, D.; Seward, C.; D’Iorio, M.; Tao, Y.; Wang, S. Dalton Trans. 2002, 3234. 25. Jia, W.-L.; Liu, Q.-D.; Wang, R.; Wang, S. Organometallics 2003, 22, 4070. 26. Jamie J. Klappa, Autumn E. Rich, and Kristopher McNeill Org. Lett., 2002, 4, 435 27. Nagata, Y.; Kanaka, H. Bull. Chem. Soc. Jpn.,2002, 75, 11 28. Yoo, C.; Oh, S.; Lee, Y. Chem. Sci., 2014, 5, 3853 91 29. Liang, L.; Hung, Y.; Huang, Y. Organometallics, 2012, 31, 700 30. Chen, C.; Hsieh, C.; Lee, H Acta Cryst. 2009. 65, 1680 31. Eisenberg, R.; Pierpont, C. Inorg. Chem. 1972, 11, 829 32. Wo¨hlert, S.; Jess, Y.; Na¨ther, C. Acta Cryst. 2011, 67, 309 33. Getsis, A.; Mudring, A. Anorg. Allg. Chem. 2008, 634, 2130 34. Fawcett, J.; Sicilia, S.; Solan, G. Acta Cryst. 2005, 61, 1256 35. Korobkov, I.; Vidjayacoumar, B.; Gorelsky, S. I.; Billone, P.; Gambarotta, S. Organometallics 2010, 29, 692. 36. Solari, E.; Crescenzi, R.; Jacoby, D.; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C. Organometallics 1996, 15, 2685. 37. Yunlu, K.; Basolo, F.; Rheingold, A. L. J. Organomet. Chem. 1987, 330, 221. 38. Liu, Q.; Thorne, L.; Kozin, I.; Song, D.; Seward, C.; D’Iorio, M.; Tao, Y.; Wang, S. Dalton Trans. 2002, 3234. 39. Jia, W.-L.; Liu, Q.-D.; Wang, R.; Wang, S. Organometallics 2003, 22, 4070. 40. Klappa, J. J.; Rich, A. E.; McNeill, K. Org. Lett. 2002, 4, 435. 41. Irving, R. J.; Magnusson, E. A. J. Chem. Soc. 1958, 2283. 42. Bollermann, T.; Gemel, C.; Fischer, R. A. Coord. Chem. Rev. 2012, 256, 43. Campbell, W. M.; Burrell, A. K.; Officer, D. L.; Jolley, K. W. Coord. Chem. Rev. 2004, 248, 1363. 44. Miedaner, A.; Curtis, C.; Wander, A.; Goodson, P.; DuBois, D. Organometallics, 1996, 15, 5185. 45. Litkenhous, E.; Mann, C. Industrial and Engineering Chemistry 1937, 934 46. Yoo, C.; Oh, S.; Kim, J.; Lee, Y. Chem. Sci., 2014, 5, 3853 47. Wrighton, M. Chem. Rev., 1974, 74, 401 48. Li, L.-L.; Diau, E. W.-G. Chem. Soc. Rev. 2013, 42, 291. 92 49. Spielmann, J.; Piesik, D.; Wittkamp, B.; Jansen, G.; Harder, S. Chem. Commun. 2009, 3455. 50. Tasker, S.; Standley, E.; Jamison, T. Nature 2014, 509, 299 51. Anantharaman, G.; Chandrasekhar, V.; Nehete, U. N.; Roesky, H. W.; Vidovic, D.; Magull, J. Organometallics 2004, 23, 2251. 52. Anantharaman, G.; Roesky, H. W.; Schmidt, H.-G.; Noltemeyer, M.; Pinkas, J. Inorg. Chem. 2003, 42, 970. 53. Storre, J.; Schnitter, C.; Roesky, H. W.; Schmidt, H.-G.; Noltemeyer, M.; Fleischer, R.; Stalke, D. J. Am. Chem. Soc. 1997, 119, 7505. 54. Chakraborty, S.; Patel, Y.; Guan, H. Polyhedron 2012, 32, 30 55. Jones, L. Inorg. chem. 1967, 6, 1269 56. Baiz, C.; Mcrbbie, P.; Anna, J.; Jeva, E. Kubarych, K. Acc. Chem. Res. 2009, 42, 1395 57. Hao, H.; Bhandari, S.; Ding, Y.; Roesky, H. W.; Magull, J.; Schmidt, H.G.; Noltemeyer, M.; Cui, C. Eur. J. Inorg. Chem. 2002, 5, 1060. 58. Liaw, W.; Chen, C.; Lee, C.; Lee, G.; Peng, S. Dalton Trans, 2001, 138 59. Searles, K.; Das, A. K.; Buell, R. W.; Pink, M.; Chen, C.-H.; Pal, K.; Morgan, D. G. Mindiola, D. J.; Caulton, K. G. Inorg. Chem. 2013, 52, 5611. 60. Clapham, S. E.; Hadzovic, A.; Morris, R. H. Coord. Chem. Rev. 2004, 248, 2201. 61. Trout, W. J. Chem. Edu., 1938, 113 62. Gao, X.; Mao, H.; Lu, M.; Yang, J.; Li, B. Microporous and Mesoporous Materials. 2012, 148, 25. 63. Noyori, R.; Koizumi, M.; Ishii, D.; Ohkuma, T. Pure Appl. Chem. 2001, 73, 93 227. 64. Aoki, T.; Ichikawa, T.; Miyaoka, H.; Kojima, Y. J. Phys. Chem. C. 2014, 118, 18412. 65. Umehara, K.; Kuwata, S.; Ikariya, T. J. Am. Chem. Soc. 2013, 135, 6754. 66. Hao, J.; Vabre, B.; Mougang-Soume, B.; Zargarian, D. Chem. Eur. J. 2014, 20, 12544. 67. Schohe-Loop, R.; Seidel, P.-r.; Bullock, W.; Feurer, A.; Terstappen, G.; Schuhmacher, J.; Vander Staay, F.-j.; Schmidt, B.; Fanelli, R. J.; Chisholm, J. C.; McCarthy, R. T. US Patent 5756517, 1998. 68. Tridentate, Dianionic Ligands for Alkane Functionalization with Platinum (II) and Oxidation of Iridium(III) Hydrides with Dioxygen. – PhD Thesis, Dara Briget Williams, University of Washington 69. Komine, N.; Buell, R.; Chen, C.; Hui, A.; Pink, M.; Caulton, K. Inorg. Chem. 2014, 53, 1361 70. Synthesis, Structure and Reactivity Studies of Nickel Pincer Complexes and Evaluating Redox Non-innocence of the Ligand, PhD Thesis, Debasis Adhikari, Indiana University 71. Ameen, J.; Durfee, H. J. Chem. Edu. 1971, 48, 372 72. Concise Inorganic Chemistry, Fifth Edition, J. D. Lee, Page no 422 94 Biographical Information Abhijit was born and grew up in West Bengal, India. He received his B.Sc. and M.Sc. degree in Chemistry from Vidyasagar University, India. There he worked on organic synthesis and methodologies. He studied synthesis and reactivities of substituted dihydropyrimidines with a focus on Biginelli reaction under the guidance of Dr. Sudhir Chandra Pal. Then Abhijit worked as a Junior Research Fellow for 1.5 years at Department of Organic Chemistry in Indian Association for the Cultivation of Science, Kolkata, India in the research group of Dr. Saswati Lahiri. There he worked on organic synthesis and photochemistry. In Fall 2011, Abhijit joined Department of Chemistry and Biochemistry at UT Arlington. In Spring 2012 he joined Dr. Rasika Dias group and worked on the project discussed in this thesis. Besides research, he likes to socialize and spend time in gymnasium. 95