N-Heterocyclic Carbenes in Transition Metal Catalysis and Organocatalysis

N-Heterocyclic Carbenes in Transition Metal Catalysis and Organocatalysis
Author: Catherine S.J. Cazin
Publisher: Springer Science & Business Media
Total Pages: 348
Release: 2010-10-04
Genre: Science
ISBN: 9048128668

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N-Heterocyclic Carbenes in Transition Metal Catalysis and Organocatalysis features all catalytic reactions enabled by N-heterocyclic carbenes (NHCs), either directly as organocatalysts or as ligands for transition metal catalysts. An explosion in the use of NHCs has been reported in the literature during the past seven years making this comprehensive overview highly apropos. The book begins with an introductory overview of NHCs which could have been subtitled all you need to know about NHCs. The main body of the book is dedicated to applications of NHCs in catalysis. In addition to the success stories of NHCs in metathesis, NHCs in cross coupling and more recently NHCs in organocatalysis, all other less publicized areas are also covered. As the success of NHCs is generally attributed to their potential to stabilize metal centres, the inclusion of a chapter on the decomposition of NHC catalysts is pertinent. The book closes with a chapter describing the applications of NHCs in industrial processes, which is the first coverage of its kind, and brings a unique industrial context to this book. Included in this book: Historical aspects of NHCs Synthetic pathways to NHC precursors, free NHCs and complexes Methods of characterisation of NHCs and related complexes Electronic properties of NHCs Steric properties of NHCs and models for their description NHCs for metathesis and cross-coupling reactions NHCs as organocatalysts NHC Transition-Metal mediated oxidations, additions to multiple bonds, polymerisation and oligomerisation, cyclisations, direct arylations, reactions involving CO, C-F and C-H bond activation, ... Decomposition of NHC-containing catalysts Industrial applications involving NHC-containing catalysts N-Heterocyclic Carbenes in Transition Metal Catalysis and Organocatalysis provides a fresh view of NHCs since most contributors are young emerging researchers in the field of homogeneous catalysis using NHCs. This group of contributors is complemented by highly established academic researchers and an industrialist. This book is comprehensive, from the basic features of NHCs to the latest advances, hence it is suitable for both the novice and the expert.

N-Heterocyclic Carbenes in Transition Metal Catalysis

N-Heterocyclic Carbenes in Transition Metal Catalysis
Author: Frank Glorius
Publisher: Springer
Total Pages: 240
Release: 2007-02-05
Genre: Science
ISBN: 3540369309

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In this book leading experts have surveyed major areas of application of NHC metal complexes in catalysis. The authors have placed a special focus on nickel- and palladium-catalyzed reactions, on applications in metathesis reactions, on oxidation reactions and on the use of chiral NHC-based catalysts. This compilation is rounded out by an introductory chapter and a chapter dealing with synthetic routes to NHC metal complexes.

N-heterocyclic Carbenes

N-heterocyclic Carbenes
Author: Silvia Díez-González
Publisher: Royal Society of Chemistry
Total Pages: 469
Release: 2011
Genre: Science
ISBN: 1849730423

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Over the last fifteen years, N-heterocyclic carbenes (NHCs) have mostly been used as ancillary ligands for the preparation of transition metal-based catalysts. Compared to phosphorus-containing ligands, NHCs tend to bind more strongly to metal centres, avoiding the necessity for the use of excess ligand in catalytic reactions. The corresponding complexes are often less sensitive to air and moisture, and have proven remarkably resistant to oxidation. Recent developments in catalysis applications have been facilitated by the availability of carbenes stable enough to be bottled, particularly for their use as organocatalysts. This book shows how N-heterocyclic carbenes can be useful in various fields of chemistry and not merely laboratory curiosities or simple phosphine mimics. NHCs are best known for their contribution to ruthenium and palladium-catalysed reactions but the scope of this book is much broader. The synthesis of NHC ligands and their corresponding metal complexes are covered in depth. Moreover, the biological activity of NHC-containing complexes, as well as an overview of their theoretical aspects are included. Such metal species are further examined, not only in terms of their catalytic applications, but also of their stereoelectronic parameters and reactivity/stability. Finally, special attention is given to the hot topic of organocatalysis. The book will be of interest to postgraduates, academic researchers and those working in industry.

Ligand Platforms in Homogenous Catalytic Reactions with Metals

Ligand Platforms in Homogenous Catalytic Reactions with Metals
Author: Ryohei Yamaguchi
Publisher: John Wiley & Sons
Total Pages: 358
Release: 2014-10-15
Genre: Technology & Engineering
ISBN: 1118943090

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Serving as a user's manual for synthetic organic and catalytic chemists, this book guides chemists in the design and choice of ligands to catalyze organic reactions and apply the results for more efficient, green, and practical synthesis. • Focuses on the role of ligands in metal complexes that catalyze green organic transformations: a hot topic in the area of organic synthesis and green chemistry • Offers a comprehensive resource to help readers design and choose ligands and understand selectivity/reactivity characteristics • Addresses a gap by taking novel ligand approaches and including up-to-date discussion on hydrogen transfers and reactions • Presents important industrial perspective and provides rational explanations of ligand effects, impacts, and novelty

Functionalised N-Heterocyclic Carbene Complexes

Functionalised N-Heterocyclic Carbene Complexes
Author: Olaf Kühl
Publisher: John Wiley & Sons
Total Pages: 364
Release: 2010-02-02
Genre: Science
ISBN: 0470685840

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N-heterocyclic carbenes (NHCs) have found increasing use as reagents for a range of organic transformations and in asymmetric organocatalysis. The performance of these molecules can be improved and tuned by functionalisation. Functionalised carbenes can anchor free carbenes to the metal site, introduce hemilability, provide a means to immobilise transition metal carbene catalysts, introduce chirality, provide a chelate ligand or bridge two metal centres. NHC can be attached to carbohydrates and campher, derived from amino acids and purines, they can be used as organocatalysts mimicking vitamin B1 or as weak “solvent” donors in lanthanide chemistry. Functionalised N-Heterocyclic Carbene Complexes describes major trends in functionalised NHC ligands, aiming to assist readers in their attempts to develop and apply their own functionalised carbenes. After an introduction to the chemistry and behaviour of NHC, the book gives a detailed description of functionalised carbenes and their complexes according to a range of functional groups, each with a discussion of the synthetic route, structure, stability and performance. Functionalised N-Heterocyclic Carbene Complexes is an essential guide to fine-tuning this important class of compounds for practitioners, researchers and advanced students working in synthetic organometallic and organic chemistry and catalysis.

Electronic Effects in Multidentate Pyridinol and N-Heterocyclic Carbene Based Ligands for Transition Metal Catalyzed Carbon Dioxide Reduction

Electronic Effects in Multidentate Pyridinol and N-Heterocyclic Carbene Based Ligands for Transition Metal Catalyzed Carbon Dioxide Reduction
Author: Chance M Boudreaux
Publisher:
Total Pages:
Release: 2021
Genre: Electronic dissertations
ISBN:

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The design of new catalysts with high catalytic efficiency and robustness towards carbon dioxide (CO2) reduction is of paramount importance. A full understanding of the requirements for creating a catalyst of this type is a missing gap in the knowledge base which prevents progress in synthesizing solar fuels. Our research hypothesis is that through the control of steric and electronic factors we can design better catalysts using various transition metals. Multidentate ligands composed of pyridyl bound to N-heterocyclic carbene rings are a synthetically flexible scaffold capable of testing our hypotheses. The systematic tuning of this scaffold will elucidate the factors necessary to improve active catalysts and extend our results to more complex systems. These ligand motifs are also commonly seen in many active catalysts for CO2 reduction. Therefore, the systemic investigation of the properties that lead to higher activity in scaffolds containing these motifs can concurrently suggest improvements for many systems already available.Reduction catalysts, supported by a CNC-pincer moiety, are some of the most robust catalysts in the literature while maintaining good catalytic activity. The CNC-pincer scaffold have shown tremendous results with electronic tunability of the pyridyl N atom through para substitution of the pyridinol ring. A ruthenium(II) catalyst utilizing the CNC pincer has shown 250 turn-over numbers of carbon monoxide (CO) over 40 h with a catalyst loading of 100 ℗æM. The cobalt(I) systems are slower; however, they are even more robust than the ruthenium analog producing 203 TON of CO2 over 72 h with a catalyst loading of 1 ℗æM. Notably, the cobalt catalyst utilizes an inexpensive, less toxic, and earth abundant metal center compared to ruthenium. Another scaffold, with NCCN donors binding in a tetradentate fashion, is currently being investigated with nickel(II) and cobalt(II) metal centers. These studies are producing a better understanding of the catalyst structure needs for a solar to chemical fuel catalyst to enable a carbon-neutral fuel cycle within our current fuel infrastructure. This catalytic system will constitute an artificial photosynthesis scheme by producing fuels and other useful chemicals from carbon dioxide, mimicking how plants store solar energy in glucose.

Late Transition Metal Complexes Incorporating Hemilabile Mixed-donor N-heterocyclic Carbene Ligands

Late Transition Metal Complexes Incorporating Hemilabile Mixed-donor N-heterocyclic Carbene Ligands
Author:
Publisher:
Total Pages:
Release: 2004
Genre:
ISBN:

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The discovery of N-heterocyclic carbenes (NHC) has dramatically affected the world of catalysis. Their inherent properties that make them excellent auxiliary ligands for catalytic processes have countless laboratories worldwide probing and exploiting every notable feature they possess. However, while there is no shortage of attention in this field of research, there has been considerably less interest in NHCs with an ability chelate to metals via a mixed-donor ligand architecture. Thus, this thesis describes the synthesis and application of a ligand set comprised of bidentate mixed-donor NHC ligands. The ligands prepared all contain a mesitylimidazol-2-ylidene core unit, but incorporate different donor-functionalized tethers. These mixed-donor NHC ligands are synthesized by using a strong base, such as KN(SiMe3)2, to deprotonate the imidazolium salt precursors. This strategy was used to effectively prepare 1-mesityl-3-(2-(mesitylamino)ethyl)imidazol-2-ylidene, Mes[CNH] and 1-mesityl-3-(2-aminoethyl)imidazol-2-ylidene, Mes[CNH2]. Mes[CNH] was found to be a convenient proligand for the synthesis of various M-NHC (M = Rh, Ir, Ru, Pd, Ni, Fe, Ag, Li) compounds. These Mes[CNH]-M complexes demonstrated the hemilabile character of the Mes[CNH] ligand forming complexes that incorporated either a coordinated or uncoordinated amino tether. Mes[CNH]M(diene)Cl, Mes[CN]M(diene) and [Mes[CNH]M(diene)]BF4(M = Rh, Ir; diene = 1,5-cyclooctadiene, 2,5-norbornadiene) were synthesized and investigated for their ability to perform hydrogenation and hydrosilylation reactions with various substrates. Mes[CNH]Ru(=CHPh)(PCy3)Cl2, Mes[CNH]Ru(=CHPh)(py)Cl2 (py = pyridine) and Mes[CNH]Ru(=CHPh)(PMe3)Cl2 were also synthesized and fully characterized. The activity of the former two Ru complexes was studied for their ability to catalyze ring-closing metathesis (RCM) and ring-opening metathesis polymerization (ROMP) reactions. In addition, the phosphine dissociation rate of Mes[CNH]Ru(=CHPh)(PCy3).

Transition Metal Complexes of Neutral Eta1-Carbon Ligands

Transition Metal Complexes of Neutral Eta1-Carbon Ligands
Author: Remi Chauvin
Publisher: Springer Science & Business Media
Total Pages: 260
Release: 2010-01-12
Genre: Science
ISBN: 3642047211

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This book is part of a series that gives the broad scientific readership a comprehensive summary and critical overview of specific topics in the field of organometallic chemistry. This text focuses on transition metal complexes of neutral eta1-carbon ligands.

The Organometallic Chemistry of N-heterocyclic Carbenes

The Organometallic Chemistry of N-heterocyclic Carbenes
Author: Han Vinh Huynh
Publisher: John Wiley & Sons
Total Pages: 334
Release: 2017-04-17
Genre: Science
ISBN: 1118593774

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The Organometallic Chemistry of N-heterocyclic Carbenes describes various aspects of N-heterocyclic Carbenes (NHCs) and their transition metal complexes at an entry level suitable for advanced undergraduate students and above. The book starts with a historical overview on the quest for carbenes and their complexes. Subsequently, unique properties, reactivities and nomenclature of the four classical NHCs derived from imidazoline, imidazole, benzimidazole and 1,2,4-triazole are elaborated. General and historically relevant synthetic aspects for NHCs, their precursors and complexes are then explained. The book continues with coverage on the preparation and characteristics of selected NHC complexes containing the most common metals in this area, i.e. Ni, Pd, Pt, Ag, Cu, Au, Ru, Rh and Ir. The book concludes with an overview and outlook on the development of various non-classical NHCs beyond the four classical types. Topics covered include: Stabilization, dimerization and decomposition of NHCs Stereoelectronic properties of NHCs and their evaluation Diversity of NHCs Isomers of NHC complexes and their identification NMR spectroscopic signatures of NHC complexes normal, abnormal and mesoionic NHCs The Organometallic Chemistry of N-heterocyclic Carbenes is an essential resource for all students and researchers interested in this increasingly important and popular field of research.