Download or read book Synthesis Toward N heterocyclic Carbene Diarylthiolate Pincer Ligands and Their Transition Metal Complexes written by Ryan Cheng and published by . This book was released on 2011 with total page 102 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 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 of Bifunctional Pincer Metal Complexes Containing N heterocyclic Carbenes written by Derek B. Brown and published by . This book was released on 2010 with total page 63 pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of this research is to synthesize pincer ligands and complexes with a central pyridine ligand substituted at positions 2 and 6 by two N-heterocyclic carbenes, each bearing a pendant heteroaryl substituent. Related pincers without heteroaryl groups have been reported in the past 15 years as catalysts, and our ultimate goal was to enable the study of the heteroaryl moieties as pendant bases, creating improved bifunctional catalysts. Two classes of pincers were made: one with methylene spacers between the central pyridine and the imidazol-2-ylidene groups, and those whose imidazol-2-ylidene groups were attached directly to the pyridine without any spacers. Four bis(imidazolium) salt pincer precursors with methylene spacers were made, and reaction with Ag2O produced silver-carbene complexes which act as transmetallation agents for further complexation. Two of the analogs were able to be metallated with (COD)PdCl2 to form palladium-carbene complexes, NMR data for which are in accord with a puckered structure induced by the methylene spacers. One of these complexes showed catalytic activity in the Heck coupling reaction. Synthesis of analogs lacking spacers under literature conditions proved to be impossible, presumably because of reduced nucleophilicity of 1-heteroarylimidazoles. Thus, a systematic study of reactivity of 1-substituted imidazoles with five 2,6-disubstituted pyridines conclusively showed that 2,6-bis(trifluoromethanesulfonyloxy)pyridine (16) was the best precursor. A well-described synthesis of 16 was developed, paving the way to making seven analogs of pincer precursors without methylene spacers. Reaction of two of these pincer precursors with Ag2O and NaOH produced silver-carbene bridged-dimer complexes which were characterized by X-ray diffraction and show promise as sources of other metal complexes.
Download or read book N Heterocyclic Carbenes in Transition Metal Catalysis written by Frank Glorius and published by Springer. This book was released on 2010-11-19 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Transition Metal Complexes of N heterocyclic Carbenes and Derivatives Thereof written by Timothy Gordon Larocque and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: N-heterocyclic carbenes (NHCs) have played a dominant role in organometallic chemistry for decades and revolutionized the field of homogenous catalysis. NHCs have been thoroughly studied, both experimentally and theoretically, and have shown unique reactivity towards transition metals, chalcogens, azides and pnictogens. This thesis is aimed at utilizing the unique reactivity of N-heterocyclic carbenes to develop novel, robust catalysts to mediate organic transformations. The multi-faceted work within this thesis explores the use of NHCs as ancillary ligands on early and late transition metals as potential catalysts for olefin polymerization and ring-closing metathesis, respectively. This work also includes exploring the synthesis and coordination of ancillary ligands derived from the unique reactivity of NHCs towards azides, chalcogens and pnictinidenes. The reactivity of a novel aryl-substituted acyclic imino-N-heterocyclic carbene to early transition metals, cyclooctasulfur and Grubbs-type ruthenium benzylidene complexes was explored. The reactivity of imidazol-2-imide towards Grubbs-type ruthenium benzylidene complexes and the synthesis and coordination of a novel group of ligands bearing an imidazol-2-imine scaffold were also explored. Lastly, this work will include the reactivity of IMes=PPh to Grubbs-type ruthenium benzylidene complexes.
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 Synthesis of Transition Metal N heterocyclic Carbene Complexes and Applications in Catalysis written by Michael Holtz-Mulholland and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Late Transition Metal Complexes Incorporating Hemilabile Mixed donor N heterocyclic Carbene Ligands written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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).
Download or read book Aryl Substituted Imino N Heterocyclic Carbene Complexes Of Late Transition Metals written by Anna Candace Badaj and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Metal Complexes of Tripodal N heterocyclic Carbene Ligands written by Xile Hu and published by . This book was released on 2004 with total page 496 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Science of Synthesis N Heterocyclic Carbenes in Catalytic Organic Synthesis written by Steven P. Nolan and published by . This book was released on 2016-12 with total page 522 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book N Heterocyclic Carbene Metal Complexes written by Haw-Lih Su and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: N-Heterocyclic carbenes (NHCs) are good ligands to most transition metals forming stable complexes. Many of the NHC-metal complexes are now widely used catalysts. However, the usage of these catalysts encounters the general problems associated with homogeneous catalysis: the purification of the catalysis reaction products is often time-consuming and generates large amounts of waste. Moreover, the toxic or expensive catalysts are difficult to be separated, recycled, and reused. Chapters II and III of this dissertation focus on addressing these problems through the development of an easier and "greener" process to improve the usage of some NHC-metal complexes. Polymer-supported catalysts and polymer-supported sequestrants were prepared and used to facilitate the separation/recycling of catalysts and the purification of products. These polymer-supported ligands, catalysts, and sequestrants showed comparable reactivity to their low molecular weight counterparts and had different solubility properties due to the nature of polymers. Using these materials with the corresponding operations provides simple methods to separate deeply colored, metal-containing by-products from the reaction mixtures. Chapter IV of this dissertation aims at solving a fundamental question about the nature of NHC-silver(I) complexes. The NHC-silver(I) complex is an important synthetic intermediate as it can be used to prepare other NHC-metal complexes through transmetallation. The carbene carbon of an NHC-silver(I) complex in 13C NMR spectra was usually reported as a doublet of doublets or as a singlet in different cases. This phenomenon was explained with a ligand exchange mechanism proposed twelve years ago. However, few reports are available in the literature about the mechanism of the NHC ligand exchange processes at silver. In order to facilitate the study of the solution behaviors of NHC-silver(I) complexes, 13C-labeled NHC-silver(I) complexes were prepared and studied using variable temperature 13C NMR spectroscopy. This study could be useful for future applications of ligand transferring from silver to other metals for the preparation of NHC-metal complexes.
Download or read book Synthesis of Electron Deficient N heterocyclic carbenes and Activity of Imidazol 2 imine Thioureate Ligand on Group 10 Transition Metals written by Michael Byron Harkness and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Transition Metal Complexes of Bis carbene pyridine pincer Ligands written by David Charles Pugh and published by . This book was released on 2008 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Transition Metal Complexes of N Anchored N Heterocyclic Carbene Ligands Synthesis Characterization and Reactivity written by Eva Zolnhofer and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Synthesis and Structural and Catalytic Investigation of N heterocyclic Carbene Metal Complexes Derived from Electron rich Alkoxybenzimidazolin 2 ylidenes written by Peter Vernon Simpson and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents an investigation into the synthesis, properties and application of a series of transition metal complexes bearing N-heterocyclic carbene ligands. There were four main areas of focus: the synthesis of alkoxy functionalised benzimidazolium salts and the assessment of their electron-donating abilities; the synthesis of transition metal complexes bearing electron-rich N-heterocyclic carbene ligands, and an investigation of their properties; an investigation into the catalytic activity of the palladium and rhodium complexes; and a preliminary study into the possibility of immobilising a palladium- NHC complex onto silica gel for use as a solid-supported heterogeneous catalyst. Various butoxy-functionalised benzimidazolium salts, including mono- (benzimidazolium) salts, bis(benzimidazolium) salts and benzimidazolium cyclophanes were prepared as precursors to electron rich NHC-metal complexes. Preparation of the (NHC)RhI(CO)2 complexes I - III and subsequent analysis by IR spectroscopy confirmed the increased electron richness of the butoxy-functionalised NHCs compared to the non-butoxy-functionalised analogues. Some of the benzimidazolium salts were used to prepare Ag(I)-NHC complexes for the purpose of transmetallation agents. Treatment of the Ag(I)-NHC complex IV with [RuCl2(p-cymene)]2 yielded the dinuclear cationic Ru(II)-NHC complex V, which exhibits !2-binding of the quaternary carbons of each xylyl ring to the Ru centre. This unique complex was also converted to the hexafluorophosphate complex in excellent yields. A range of Pd(II)-NHC complexes were synthesized. The complexes possessed mono(NHC), chelating bis(NHC) (bridged on one or both sides), and mixed NHC/ancillary ligand systems, in order to assess the most favourable structural characteristics of a potential catalyst. Reaction of the bis(benzimidazolium) salt VI with Pd(OAc)2 gave two complexes, VII and VIII, which were subsequently isolated. The unusual complex VII, in which the xylyl ring is folded under the metal centre, was found to isomerise to IX over approximately twenty-six days in CDCl3. The conformations of the xylyl ring in VII and IX was confirmed using selective NOESY experiments. Two trans-o-xylyl-linked Pd(II)-NHC complexes were prepared and characterised, and represent the only fully characterised complexes of this type. During efforts to synthesize the dinitrophenyl-functionalised bis(NHC)-Pd(II) complex X under strict anhydrous and anaerobic conditions, instead, the trinuclear Abstract v palladium complex XI was isolated, where one dinitrophenyl group of each ligand has been displaced, presumably by attack from adventitious water or acetate present in the reaction mixture. Pd N N N N Br. Many of the Pd(II)-NHC complexes were tested in an extensive set of experiments designed to provide an insight into favourable structural motifs for a potential catalyst and confirm the beneficial nature of the electron donating butoxy groups. It was found that the Pd(II)-NHC complexes possessing chelating bis(NHC) ligands were the most active in the Mizoroki-Heck and Suzuki-Miyaura cross-coupling reactions, possibly due to the robustness of these complexes at the temperatures necessary to promote the reactions. Gratifyingly, the complexes possessing butoxy groups were found to be more active than the non-butoxy-functionalised analogues.
