Download or read book Synthesis and Structural Characterization of CCC N Heterocyclic Carbene CCC NHC Pincer Complexes of Nickel written by Paul Jerome Kelley and published by . This book was released on 2010 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: The recently reported methodology for concomitant triple C-H activation of a CCC-NHC pincer ligand precursor followed by transmetallation to late transition metals has been extended to include nickel. A very faint solid state fluorescence has been collected for the complexes reported. X-ray structural analysis of a representative compound exhibits a distorted square planar geometry. Issues with rapid halogen exchange have been found in some cases indicating increased liability of the halide ligand uncommon in comparable systems.
Download or read book Design Synthesis and Characterization of Chiral CCC NHC Transition Metal Complexes and Catalytic Activity written by Gopalakrishna Akurathi and published by . This book was released on 2016 with total page 177 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first stable "free" N-heterocyclic carbene (NHC) was isolated in 1991, since then many classes of NHCs were synthesized and isolated. N-heterocyclic carbene ligands have become a common ligand in the synthesis of metal complexes, due to their strong [Sigma]-donation with poor [pi]-acceptor ability. Among all the NHC metal complexes, Hollis group was interested in exploring CCC-NHC pincer complexes. In 2005, Hollis and co-workers synthesized and isolated first achiral CCC-NHC zirconium pincer amido complex and studied its catalytic ability to perform intramolecular hydroamination of aminoalkenes. Later, Hollis group designed and developed new NHCs with a saturated chiral backbone, and used these new ligands to generate a new series of metal complexes. This dissertation is focused on the design, synthesis and characterization of several chiral bi-dentate NHC ligands with varying substituents on the backbone. These NHC ligands were used to synthesize several chiral mono, bis and tris amido CCC-NHC zirconium pincer complexes. Further, transmetallation to cobalt complexes were achieved. Intramolecular hydroamination was measured for several chiral bis and tris amido CCC-NHC pincer zirconium catalysts. Variants of these catalytic systems were generated with differing steric hinderance and electronic structure. The enantioselectivity of these novel new molecules were studied.
Download or read book N heterocyclic Carbene Complexes of Ag I and Zr IV written by Wesley D. Clark and published by . This book was released on 2015 with total page 317 pages. Available in PDF, EPUB and Kindle. Book excerpt: The synthesis and characterization of the first series of tetra-NHC-Ag(I)-X cubane clusters are reported. The clusters were characterized with 1H and 13C NMR spectroscopy, ESI-TOF MS, and single crystal X-ray diffraction. Crossover experimental data were consistent with intramolecular exchange, which can be visualized by a molecular rotating type mechanism. Additionally, CCC-NHC Zr(IV) pincer type complexes were synthesized and characterized with 1H and 13C NMR spectroscopy, CHN combustion analysis, and X-ray crystallography. A large rate effect was observed based on the halogen and metal center for the hydroamination/cyclization of unactivated aminoalkenes. Zirconium based pincers provided faster reaction rates than their hafnium counterparts (Zr>Hf). Precatalysts with iodide ligands provided faster reaction rates than their bromide and chloride counterparts (I>Br>Cl). The mechanism of hydroamination for Zr(IV) CCC-NHC complexes was also investigated for bis(iodide) and bis(amido) ligand classes. A full kinetic analysis of substrate and precatalyst have been identified along with the formation of small amounts of an oxidized product. The proposed mechanism contains an imido-type intermediate whose formation depends greatly on which set of ligand class is used.
Download or read book Synthesis and Characterization of a CCC NHC Manganese Complex and Its Catalytic Activity in Alpha alkylation Reactions of Ketones Using Alcohols Acceptorless Dehydrogenative Coupling Reaction written by Thi Bao Tran Nguyen and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: N-heterocyclic carbenes are essential for the synthesis and stabilization of various metal complexes due to the tendency to act as sigma-donor of sp2 hybridized lone pair in carbene into sigma-accepting orbital of metals. Meanwhile, the electronic and steric properties of pincer complexes can be fine-tuned by modifying three sites bonded to the metals. Utilizing advantages of both NHCs and the pincer structures, NHCs-based pincer complexes have become increasingly developed in recent years. After the discovery of zirconium and rhodium complexes with CCC-NHC backbones reported in 2005, Hollis’s group has been interested in applying the CCC-NHC pincer precursor for other transition metals. Manganese, the third most abundant transition metal in the earth’s crust, has lower cost and less toxic features compared to most of the others. Herein, the CCC-NHCs manganese pincer complex is synthesized and characterized and its catalytic activity in alpha- alkylation reaction of ketones using alcohols was studied.
Download or read book Pincer Compounds written by David Morales-Morales and published by Elsevier. This book was released on 2018-04-11 with total page 756 pages. Available in PDF, EPUB and Kindle. Book excerpt: Pincer Compounds: Chemistry and Applications offers valuable state-of-the-art coverage highlighting highly active areas of research—from mechanistic work to synthesis and characterization. The book focuses on small molecule activation chemistry (particularly H2 and hydrogenation), earth abundant metals (such as Fe), actinides, carbene-pincers, chiral catalysis, and alternative solvent usage. The book covers the current state of the field, featuring chapters from renowned contributors, covering four continents and ranging from still-active pioneers to new names emerging as creative strong contributors to this fascinating and promising area. Over a decade since the publication of Morales-Morales and Jensen’s The Chemistry of Pincer Compounds (Elsevier 2007), research in this unique area has flourished, finding a plethora of applications in almost every single branch of chemistry—from their traditional application as very robust and active catalysts all the way to potential biological and pharmaceutical applications. Describes the chemistry and applications of this important class of organometallic and coordination compounds Includes contributions from global leaders in the field, featuring pioneers in the area as well as emerging experts conducting exciting research on pincer complexes Highlights areas of promising and active research, including small molecule activation, earth abundant metals, and actinide chemistry
Download or read book The Organometallic Chemistry of N heterocyclic Carbenes written by Han Vinh Huynh and published by John Wiley & Sons. This book was released on 2017-02-03 with total page 352 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Chemistry of Iron written by J. Silver and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 316 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is designed to be of use to the reader in two different ways. First, it is intended to provide a general introduction to all aspects of iron chemistry for readers from a variety of different scientific backgrounds. It has been written at a level suitable for use by graduates and advanced undergraduates in chemistry and biochemistry, and graduates in physics, geology, materials science, metallurgy and biology. It is not designed to be a dictionary of iron compounds but rather to provide each user with the necessary tools and background to pursue their ,individual interests in the wide areas that are influenced by the chemistry of iron. To achieve this goal each chapter has been written by a contemporary expert active in the subject so that the reader will benefit from their individual insight. Although it is generally assumed that the reader will have an understanding of bonding theories and general chemistry, the book is well referenced so that any deficiencies in the reader's background can be addressed. The book was also designed as a general reference book for initial pointers into a scientific literature that is growing steadily as the understanding and uses of this astonishingly versatile element continue to develop. To meet this aim the book attempts some coverage of all aspects of the chemistry of iron, not only outlining what understanding has been achieved to date but also identifying targets to be aimed at in the future.
Download or read book Nickel Catalysis in Organic Synthesis written by Sensuke Ogoshi and published by John Wiley & Sons. This book was released on 2020-03-09 with total page 348 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive reference to nickel chemistry for every scientist working with organometallic catalysts Written by one of the world?s leading reseachers in the field, Nickel Catalysis in Organic Synthesis presents a comprehensive review of the high potential of modern nickel catalysis and its application in synthesis. Structured in a clear and assessible manner, the book offers a collection of various reaction types, such as cross-coupling reactions, reactions for the activation of unreactive bonds, carbon dioxide fixation, and many more. Nickel has been recognized as one of the most interesting transition metals for homogeneous catalysis. This book offers an overview to the recently developed new ligands, new reaction conditions, and new apparatus to control the reactivity of nickel catalysts, allowing scientists to apply nickel catalysts to a variety of bond-forming reactions. A must-read for anyone working with organometallic compounds and their application in organic synthesis, this important guide: -Reviews the numerous applications of nickel catalysis in synthesis -Explores the use of nickel as a relatively cheap and earth-abundant metal -Examines the versatility of nickel catalysis in reactions like cross-coupling reactions and CH activations -Offers a resource for academics and industry professionals Written for catalytic chemists, organic chemists, inorganic chemists, structural chemists, and chemists in industry, Nickel Catalysis in Organic Synthesis provides a much-needed overview of the most recent developments in modern nickel catalysis and its application in synthesis.
Download or read book N Heterocyclic Carbenes in Synthesis written by Steven P. Nolan and published by John Wiley & Sons. This book was released on 2006-10-27 with total page 330 pages. Available in PDF, EPUB and Kindle. Book excerpt: This first handbook to focus solely on the application of N-heterocyclic carbenes in synthesis covers metathesis, organocatalysis, oxidation and asymmetric reactions, along with experimental procedures. Written by leading international experts this is a valuable and practical source for every organic chemist.
Download or read book Advances in Organometallic Chemistry written by and published by Academic Press. This book was released on 2015-06-05 with total page 307 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains authoritative reviews regarding the field of organometallic chemistry. It covers topics in organometallic synthesis, reactions, mechanisms, homogeneous catalysis, and more, and will benefit a wide range of researchers involved in organometallic chemistry, including synthetic protocols, mechanistic studies, and practical applications. Contributions from leading authorities Informs and updates on all the latest developments in the field Carefully edited to provide easy-to-read material
Download or read book The Development of Next Generation Architectures for CCC N heterocyclic Carbene Pincer Ligands written by Tyler Owen Howell and published by . This book was released on 2014 with total page 97 pages. Available in PDF, EPUB and Kindle. Book excerpt: Methodologies for expanding the architectural diversity of CCC-N-heterocyclic carbene (NHC) pincer ligand precursors and transition metal complexes have been developed for the production of more efficient catalyst, which will be employed in the synthesis of pharmaceuticals. An efficient route for the synthesis and isolation of bis-1,3-(3'-aryl-N-heterocycl-1'-yl)arenes has been established, and preliminary data for metalation and transmetalation of a N, N'-diaryl imidazolium salt has been acquired. Additionally, a proficient methodology for the synthesis of mixed, unsymmetrical CCC-NHC pincer ligand precursors has been discovered, and preliminary data for mixed, unsymmetrical transition metal complexes is also included. These methodological expansions will lead to more efficient catalyst that decrease the expenditure of energy required for the synthesis of pharmaceuticals, thus making their synthesis more favorable for the environment and their price more affordable for consumers.
Download or read book Synthesis Characterisation and Analysis of Structurally Imposing Eight membered Ring Heterocyclic Carbenes written by Wei Lu and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The work reported in this thesis is concerned with the preparation, metal coordination and catalytic applications of expanded eight-membered N-heterocyclic carbenes. This is divided into four chapters, which cover the following areas of research. Chapter One provides the historical and literature overview of synthesis, reactions and catalysis applications for the six- and seven-membered NHCs. Structure and electronic properties of the expanded ring NHC systems are also discussed and compared with their phosphine and five-membered NHC counterparts. Chapter Two focuses on the synthesis and characterisation of symmetrical, unsymmetrical and backbone functionalised eight-membered NHC halide salts and free carbenes. The precursor salts were all prepared by the amidine route while treatment with KHMDS forms the free NHCs. The 8-NHC ring adopts a boat conformation with the backbone folded over the central NHC carbon. Their N-CNHC-N angles are large, ranging between 129° and 131°, with the attendant CNHC-N-CN-substituent angles being very small. Chapter Three describes the synthesis and characterisation of a series of Ag(I), Rh(I), Ir(I) and Ni(I) complexes. Structural analysis of silver-(8-NHC) complexes reveal that these large rings cause the aromatic substituents on the ring nitrogens to bend around and essentially enclose the Ag centre. The percentage buried volume (%Vbur) of silver complexes increases considerably as the ring size expands from 5- to 8-membered NHC, reflecting the high steric demand imposed by the larger ring systems. It was also found that the 8-Mes ligand was too large to coordinate to the [Rh/IrCl(COD)]2 dimer, only the less sterically demanding 8-o-Tol was able to form stable [Rh/IrCl(8-o-Tol)(COD)] complexes. Comparison of CO stretching frequencies for [RhCl(NHC)(CO)2] complexes with 5-, 6-, 7- and 8-membered rings reveal that 8-o-Tol is the most basic of all the NHC ligands. A series of paramagnetic (8-NHC) Ni(I) complexes were prepared also, along with their characterization and EPR analysis. Chapter Four provides the results of catalytic performances for the 8-membered NHC rhodium and iridium complexes in the transfer hydrogenation of ketones. 8-NHC nickel complexes were also tested as catalysts in Suzuki and Kumada cross-coupling reactions.
Download or read book N Heterocyclic Carbenes written by Steven P. Nolan and published by John Wiley & Sons. This book was released on 2014-07-07 with total page 690 pages. Available in PDF, EPUB and Kindle. Book excerpt: This comprehensive reference and handbook covers in depth all major aspects of the use of N-heterocyclic carbene-complexes in organic synthesis: from the theoretical background to characterization, and from cross-coupling reactions to olefin metathesis. Edited by a leader and experienced scientist in the field of homogeneous catalysis and use of NHCs, this is an essential tool for every academic and industrial synthetic chemist.
Download or read book Synthesis and Catalytic Activity of CCC NHC Group 9 Metal Pincer Complexes written by Sean William Reilly and published by . This book was released on 2015 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt: N-Heterocyclic carbenes (NHCs) are one of the few ligand systems that can finely tune transition metal catalysts via sterics and electronics. The strong sigma-donating properties of these ancillary ligands allow the development of robust tridentate NHC pincer framework, which has emerged as an alternative to the phosphine pincer ligands. The combination of NHC and pincer systems has resulted in a new generation of catalytically active organometallic complexes reported throughout the literature. CCC-NHC Rh pincer complexes were found to be catalytically active in C-C and C-B bond formation via 1,4-addition reactions. In addition, the in-situ generated CCC-NHC Ir(H) pincer complex demonstrated catalytic activity in borylation of arene C-H bonds. Preliminary results are comparable to the C-H borylation results published by Hartwig and co-workers. The CCC-NHC Ir(H) pincer complex may also prove to be a suitable catalyst for alkane dehydrogenation, due to framework similarities of the highly active and durable PCP and POCOP pincer hydride systems. Expansion of group 9 metal sources for transmetalation of the CCC-NHC Zr pincer complex afforded the development of CCC-NHC Rh(CO) and CCC-NHC Co complexes. Group 9 metal carbonyl complexes have been reported as active catalysts in photocatalytic C-H activation of small molecules. Testing of Co sources for transmetalation afforded three rare Co pincer complexes, and the first examples of CCC-NHC Co pincer complexes to date. Development of CCC-NHC pincer complexes with base metals provide cost-effect alternatives to pincer systems with precious metal centers, and is reported herein.
Download or read book The Method Development for Synthesizing Chiral CCC NHC Zr Pincer Complexes written by Amarraj Chakraborty and published by . This book was released on 2015 with total page 82 pages. Available in PDF, EPUB and Kindle. Book excerpt: There are numerous classes of N-heterocyclic carbenes (NHCs) that have been synthesized since the discovery of stable NHCs in 1988. Their application as ligands in metal complexes has received much attention because of their strong sigma-donor and poor pi-acceptor properties. Within these NHC metal complexes, we are interested in studying zirconium metal complexes with pincer NHC ligands. Recently, achiral CCC-NHC pincer zirconium complexes were synthesized and their catalytic activity in intramolecular hydroamination of aminoalkenes were reported. Herein is reported new reaction conditions which yield pure, chiral CCC-NHC Zr pincer mono(amido) dibromo complex. The enantiopure crystal structure of the same complex is reported. Attempts to synthesize chiral CCC-NHC Zr pincer bis- and tris- amido complexes with the iodo salt of the ligand precursor are summarized. Moreover, syntheses of chiral bis(imidazolinium) ligand precursors with different counter anions are reported with optimized reaction conditions.
Download or read book Nickel Bis N heterocyclic Carbene Complexes written by Mark Hill Reineke and published by . This book was released on 2017 with total page 204 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nickel is an attractive metal for use in a wide variety of catalytic transformations that normally require precious metals. Of particular interest is the reduction of CO2 to formate, which is a potential hydrogen storage medium, fuel, and chemical building block. The nickel bis-diphosphine class of complexes has recently been studied for this application. However, it has been found that existing nickel bis-diphosphine complexes cannot produce hydrides that are capable of reducing CO2 to form formate. In this dissertation, I first provide a detailed analysis of the thermodynamic relationships which are responsible for the inadequate reduction power of hydrides formed by known nickel bis-diphosphines. It is established that by designing complexes with a more negative reduction potential than that of a typical nickel bis-diphosphine complex, more powerfully reducing hydrides may be formed. N-heterocyclic carbene (NHC) ligands are chosen as a substitute for phosphine ligands in this system, as NHC ligands are generally more electron donating than typical phosphine ligands, and are thus expected to result in complexes with more negative reduction potentials. By direct analogy to known nickel bis-diphosphine complexes, homoleptic nickel bis(NHC) complexes are synthesized. These are found to form sterically hindered, highly reducing Ni(0) compounds upon reduction. These Ni(0) compounds are the first group 10 M(0) (M = nickel, palladium, platinum) tetracarbene complexes reported. They display an unusual sawhorse geometry in the Ni(0) state. In order to address the electrochemical irreversibility displayed the nickel tetracarbene complexes, a less sterically encumbering bis(NHC) ligand linked by a propyl group is chosen. This ligand is found to provide access to the [Ni(NHC2)]2+ fragment, which in turn provides access to a new Ni(II)(NHC2)¬L2 class of complexes. Four Ni(II)(NHC2)¬(bipyridine) complexes are synthesized and characterized. It is found that a rigid, twice-linked bis(NHC) ligand is capable of imparting electrochemical reversibility to these systems. This new bis(NHC) ligand is used to synthesize the first Ni(II)(NHC2)(diphosphine) complex. This compound is isolated in both the Ni(II) and Ni(0) oxidation states. Strategies to further develop this system in order to be suitable for CO2 reduction are discussed. Future experiments involving the [Ni(NHC2)]2+ fragment are also suggested.
Download or read book Functionalised N Heterocyclic Carbene Complexes written by Olaf Kühl and published by Wiley. This book was released on 2010-02-02 with total page 364 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
