Introduction 1.1 Background
... ferrocenyl as the R’ substituent, while the OR substituent would be varied systematically between an organic ethoxy group and an organometallic titanoxy group. Initially, Group VI transition metals (Cr, Mo, W) with carbonyl ligands were chosen as being representative of a class of Fischer carbene co ...
... ferrocenyl as the R’ substituent, while the OR substituent would be varied systematically between an organic ethoxy group and an organometallic titanoxy group. Initially, Group VI transition metals (Cr, Mo, W) with carbonyl ligands were chosen as being representative of a class of Fischer carbene co ...
The Other Side of NHCs: NHCs in Transition Metal Catalysis
... Olefin Metathesis: Incorporation of NHCs •NHCs are perfect candidates as ligands for Ru based metathesis. •Strong σ donation and weak π acceptor character leads to strong NHCRu bonds (5 kcal/mol greater!) •These factors, along with greater steric bulk, result in increased activity, more robust reac ...
... Olefin Metathesis: Incorporation of NHCs •NHCs are perfect candidates as ligands for Ru based metathesis. •Strong σ donation and weak π acceptor character leads to strong NHCRu bonds (5 kcal/mol greater!) •These factors, along with greater steric bulk, result in increased activity, more robust reac ...
File
... Complex of the type Pt(PR3)4 can form PtCl2 (PR3)2 when reacted with HCl: suggest an explanation for this result, including a reaction scheme naming the elementary reactions involved and showing the byproducts. ...
... Complex of the type Pt(PR3)4 can form PtCl2 (PR3)2 when reacted with HCl: suggest an explanation for this result, including a reaction scheme naming the elementary reactions involved and showing the byproducts. ...
Low oxidation state diphosphorus and diarsenic compounds
... Although the allotropes of phosphorus and arsenic have been extensively studied, the chemistry of their diatomic forms has remained elusive. The free diphosphorus molecule P2 forms only at temperatures above 800 °C, and the free diarsenic molecule As2 has never been directly observed.1 Triply bonded ...
... Although the allotropes of phosphorus and arsenic have been extensively studied, the chemistry of their diatomic forms has remained elusive. The free diphosphorus molecule P2 forms only at temperatures above 800 °C, and the free diarsenic molecule As2 has never been directly observed.1 Triply bonded ...
Introduction - University of Pretoria
... different methods: (i) transformation of a non-carbene ligand and (ii) addition of a carbene ligand precursor to a metal complex from pre-existing carbene complexes, of which five reactions are possible. They are (i) the transfer of a carbene ligand from one metal to another, (ii) modification of th ...
... different methods: (i) transformation of a non-carbene ligand and (ii) addition of a carbene ligand precursor to a metal complex from pre-existing carbene complexes, of which five reactions are possible. They are (i) the transfer of a carbene ligand from one metal to another, (ii) modification of th ...
Title Iridium, ruthenium, and palladium complexes containing a
... complexes 2 and 3 involving the palladium precursor [PdCl(allyl)]2 afforded the biscarbene complex 4 together with minor other species (Scheme 2). Attempts to use a similar transmetallation procedure with [PdCl2(NCMe)2] were not successful and the imidazolium ligand precursor was recovered. Despite ...
... complexes 2 and 3 involving the palladium precursor [PdCl(allyl)]2 afforded the biscarbene complex 4 together with minor other species (Scheme 2). Attempts to use a similar transmetallation procedure with [PdCl2(NCMe)2] were not successful and the imidazolium ligand precursor was recovered. Despite ...
Scientific abstract
... chiral substituents into monodentate imidazolylidene NHC’s. The dynamic nature of these systems, however, prevents a sufficient definition of chiral space required for asymmetric induction (Figure 1). Bidentate ligands generally create more rigid metal complexes, which may help to overcome this prob ...
... chiral substituents into monodentate imidazolylidene NHC’s. The dynamic nature of these systems, however, prevents a sufficient definition of chiral space required for asymmetric induction (Figure 1). Bidentate ligands generally create more rigid metal complexes, which may help to overcome this prob ...
Metal-Ligand Multiple Bonds
... In general, multiple bonds to silicon and other second-row main group elements are less stable than multiple bonds to carbon, oxygen and nitrogen. ex) Si=O, M=Si: unstable ...
... In general, multiple bonds to silicon and other second-row main group elements are less stable than multiple bonds to carbon, oxygen and nitrogen. ex) Si=O, M=Si: unstable ...
Chapter 2: Dative Ligands 2.1 Introduction 2.2.1. Properties of Free
... : prone to rearrange to alkyne ...
... : prone to rearrange to alkyne ...
Metal-induced tautomerization of oxazole and thiazole molecules to
... Oxazole (1a) and thiazole (1b) are simple molecules of great relevance in heterocyclic chemistry and important structural elements in many natural products.1 Their corresponding carbene tautomers, 2,3-dihydrooxazol-2-ylidene (2a) and 2,3-dihydrothiazol-2-ylidene (2b), derived from a 1,2-hydrogen shi ...
... Oxazole (1a) and thiazole (1b) are simple molecules of great relevance in heterocyclic chemistry and important structural elements in many natural products.1 Their corresponding carbene tautomers, 2,3-dihydrooxazol-2-ylidene (2a) and 2,3-dihydrothiazol-2-ylidene (2b), derived from a 1,2-hydrogen shi ...
Isolating High Value Aromatics from Lignin Stockpiles
... the BIm carbene to successfully produce the previously unreported 2-imino-1,3diisopropylbenzimidazoline; this new compound was also characterized crystallographically and can be seen in Figure 6. The reaction of all three carbenes with Br2 at -78 °C results in the precipitation of an air stable 2- b ...
... the BIm carbene to successfully produce the previously unreported 2-imino-1,3diisopropylbenzimidazoline; this new compound was also characterized crystallographically and can be seen in Figure 6. The reaction of all three carbenes with Br2 at -78 °C results in the precipitation of an air stable 2- b ...
Organometallic Compounds
... The next slides recall the diversity of nucleophiles that may be used. Observe that there is limited opportunity of creating new C-C bonds, welding together two R groups. We seem to be somewhat lacking in simple carbon based nucleophiles. ...
... The next slides recall the diversity of nucleophiles that may be used. Observe that there is limited opportunity of creating new C-C bonds, welding together two R groups. We seem to be somewhat lacking in simple carbon based nucleophiles. ...
Synthesis and Application of Functionalized NHC
... First investigated by Wanzlick and Öfele in the early 1960s,[1] N-heterocyclic carbenes (NHC’s) are a topic of high current interest, in particular in transition metal catalysis. They are an attractive alternative to phosphine ligands, thanks to their strong σ-donating capability and low level of π- ...
... First investigated by Wanzlick and Öfele in the early 1960s,[1] N-heterocyclic carbenes (NHC’s) are a topic of high current interest, in particular in transition metal catalysis. They are an attractive alternative to phosphine ligands, thanks to their strong σ-donating capability and low level of π- ...
vysoké učení technické v brně
... availability only in the form of unreactive salt, the preparation of stable reactive free NHC catalysts using Schlenk’s technique as well as its characterization by proton nuclear magnetic resonance will be depicted in the experimental part. ...
... availability only in the form of unreactive salt, the preparation of stable reactive free NHC catalysts using Schlenk’s technique as well as its characterization by proton nuclear magnetic resonance will be depicted in the experimental part. ...
Nickel(II) cis- and trans-Dimethyl Complexes of
... been prepared and characterized by single-crystal X-ray diffraction, and the complex [Ni(tBuCCmeth)Me2] (3) has been observed spectroscopically. Thermal decomposition studies show that 2 eliminates methane rapidly and quantitatively above 50 °C by a predominantly unimolecular dissociative pathway wi ...
... been prepared and characterized by single-crystal X-ray diffraction, and the complex [Ni(tBuCCmeth)Me2] (3) has been observed spectroscopically. Thermal decomposition studies show that 2 eliminates methane rapidly and quantitatively above 50 °C by a predominantly unimolecular dissociative pathway wi ...
CHAPTER 1 INTRODUCTION 1.1 Research Background
... where it was attached to a metal carrying an electron-withdrawing group(s). ...
... where it was attached to a metal carrying an electron-withdrawing group(s). ...
Sample pages 2 PDF
... The orbital scheme is similar to that of the η2-H2 complexes. In order to stabilize this kind of complexes, it is necessary to suppress the back donation of electrons from the metal to the σ* orbital of the C–H bond. This can be achieved by using d0 metal centers. This is the reason why metals like ...
... The orbital scheme is similar to that of the η2-H2 complexes. In order to stabilize this kind of complexes, it is necessary to suppress the back donation of electrons from the metal to the σ* orbital of the C–H bond. This can be achieved by using d0 metal centers. This is the reason why metals like ...
Phosphine Ligands
... Occupation of the P−R σ* orbital by back donation from the metal also implies that the P−R bonds should lengthen slightly on binding. In practice, this is masked by a simultaneous shortening of the P−R bond due to donation of the P lone pair to the metal, and the consequent decrease in P(lone pair)– ...
... Occupation of the P−R σ* orbital by back donation from the metal also implies that the P−R bonds should lengthen slightly on binding. In practice, this is masked by a simultaneous shortening of the P−R bond due to donation of the P lone pair to the metal, and the consequent decrease in P(lone pair)– ...
Pincer and Chelate N-Heterocyclic Carbene Complexes of Rh, Ir
... metal center. Theoretical and experimental work by McGuinness et al. (13) has shown that this is a viable synthetic route. In interesting recent work, Heinekey and coworkers (14) found that one C-H bond of tris(1-pyrazolyl)borate was activated by iridium to produce an NHC-like metal-carbon bond, ind ...
... metal center. Theoretical and experimental work by McGuinness et al. (13) has shown that this is a viable synthetic route. In interesting recent work, Heinekey and coworkers (14) found that one C-H bond of tris(1-pyrazolyl)borate was activated by iridium to produce an NHC-like metal-carbon bond, ind ...
Presented by Arianne Hunter
... Catalytically generated metal carbenes are highly versatile for insertion into carbon– hydrogen and heteroatom–hydrogen bonds C–H bond insertions are mechanistically different from X–H bond insertions due to their low bond polarity ...
... Catalytically generated metal carbenes are highly versatile for insertion into carbon– hydrogen and heteroatom–hydrogen bonds C–H bond insertions are mechanistically different from X–H bond insertions due to their low bond polarity ...
Lecture notes for chapter 6
... of an alkene ligand that reduces the unsaturation of the metal complex. The reverse reaction, however, also can occur and is called a migratory insertion. This is very important in transition metal reaction chemistry and catalysis, as we will see in later chapters. Note that in order to have a -hyd ...
... of an alkene ligand that reduces the unsaturation of the metal complex. The reverse reaction, however, also can occur and is called a migratory insertion. This is very important in transition metal reaction chemistry and catalysis, as we will see in later chapters. Note that in order to have a -hyd ...
Chapter 1 Structure and Bonding
... a) ZrCl4 + 4 PhCH2MgCl Zr(CH2Ph)4 b) Na[Mn(CO)5] + CH3I CH3Mn(CO)5 + NaI ...
... a) ZrCl4 + 4 PhCH2MgCl Zr(CH2Ph)4 b) Na[Mn(CO)5] + CH3I CH3Mn(CO)5 + NaI ...
lect4b
... Level-3 Organometallics L4b Complexes with -acceptor ligands There are many of these type of ligand (E/S Ch 15 S/A Ch 16) Some bond to metal through one atom - described as 1 (eta-one) ligands, while others (described later) bind through more than one. Examples of 1 ligands M-CO ...
... Level-3 Organometallics L4b Complexes with -acceptor ligands There are many of these type of ligand (E/S Ch 15 S/A Ch 16) Some bond to metal through one atom - described as 1 (eta-one) ligands, while others (described later) bind through more than one. Examples of 1 ligands M-CO ...
The catalytic hydrogenolysis of esters to the two corresponding
... since esters are very stable compounds. Therefore, the development of suitable homogeneous catalysts is very challenging. One of the current focuses in our group is the preparation of ruthenium complexes bearing tridentate ligands which consist of N-Heterocyclic Carbenes (NHCs) functionalized with p ...
... since esters are very stable compounds. Therefore, the development of suitable homogeneous catalysts is very challenging. One of the current focuses in our group is the preparation of ruthenium complexes bearing tridentate ligands which consist of N-Heterocyclic Carbenes (NHCs) functionalized with p ...
Fulltext PDF
... the carbene than in the parent imidazolium compound, indicating that there was very little double bond character to these bonds ...
... the carbene than in the parent imidazolium compound, indicating that there was very little double bond character to these bonds ...
Persistent carbene
A persistent carbene (also known as stable carbene) is a type of carbene demonstrating particular stability. The best-known examples and by far largest subgroup are the N-heterocyclic carbenes (sometimes called Arduengo carbenes), for example diaminocarbenes with the general formula (R2N)2C:, where the 'R's are typically alkyl and aryl groups. The groups can be linked to give heterocyclic carbenes, such as those derived from imidazole, imidazoline, thiazole or triazole.Traditionally carbenes are viewed as so reactive that were only studied indirectly, e.g. by trapping reactions. This situation has changed dramatically with the emergence of persistent carbenes. Although they are fairly reactive substances, i.e., undergoing dimerization, many can be isolated as pure substances.Persistent carbenes can exist in the singlet or the triplet states with the singlet state carbenes being more stable. The relative stability of these compounds is only partly due to steric hindrance by bulky groups. Some singlet carbenes are thermodynamically stable in the absence of moisture and (in most cases) oxygen, and can be isolated and indefinitely stored. Others are not thermodynamically stable and will dimerise slowly over days. The less stable triplet state carbenes have half-lives measured in seconds, and therefore can be observed but not stored.