Download or read book Development of Novel Rhodium and Iridium Complexes with a Fac chelating Ligand for Electrophilic C H Activation written by Jennifer Lee Rhinehart and published by . This book was released on 2011 with total page 218 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Several new bis-3,5(dimethylpyrazol-1-yl)acetate rhodium and iridium complexes were synthesized from MCl3?H2O. [Rh(bdmpza)Cl3]- was isolated with three different cations, lithium, sodium and tetraethylamonium, to obtain a full characterization profile. Analogously, [Ir(bdmpza)Cl3]- was isolated with two different cations, lithium and sodium, and characterized by 1H NMR, 13C NMR, elemental analysis and X-ray crystal structure determination. A neutral rhodium complex, [Rh(bdmpza)Cl2(py)], was also isolated as two isomers by addition of pyridine. Reaction of [Rh(bdmpza)Cl3]- and [Rh(bdmpza)Cl2(py)] with dimethylzinc afforded three new complexes, [Rh(bdmpza)Cl2(Me)]-, [Rh(bdmpza)Cl(Me)2]- and [Rh(bdmpza)Cl(Me)(py)]. Stoichiometric and catalytic C-H activation of benzene was investigated for these new rhodium methyl complexes. Novel rhodium and iridium precatalysts catalysts, [Rh(bdmpza)Cl3]- Na+, [Ir(bdmpza)Cl3]- Na+ and [Rh(bdmpza)Cl2(py)], were subjected to H/D exchange conditions with benzene and deuterated trifluoroacetic acid, acetic acid and methanol in the presence of a halide abstractor. Optimum conditions of silver triflate, deuterated trifuoroacetic acid, 100°C and 24 hours were identified to conduct arene H/D exchange studies. Most arenes investigated showed modest H/D exchange in the ring, while branched [beta]-sp3C-H bonds also showed affinity for H/D exchange. Mechanistic studies of [beta]-sp3C-H H/D exchange were carried out, including synthesis of [Rh(bdmpz)Cl3(py)], which does not contain the pendant acetate group"--Leaf vi.

Download or read book Synthesis of Electrophilic Rhodium and Iridium Complexes and Investigation of Reactivity for C H Bond Activation and Functionalization written by Kate E. Allen and published by . This book was released on 2013 with total page 173 pages. Available in PDF, EPUB and Kindle. Book excerpt: Direct methods for the transformation of alkanes into alcohols, alkenes, amines and other functionalized products would have a great impact on industrial processes. In this thesis the work described is aimed at developing electrophilic Rh and Ir systems to promote C-H bond activation and functionalization of alkanes and arenes. Several approaches have been taken to prepare the target complex [Tp*Ir(OH2)3]+ (Tp* = hydridotris(3,5-dimethylpyrazoyl)borate). While this species has not been synthesized, C-N coupling between ethylene and N-iodosuccinimide has been observed during the course of this study and is promoted by Tp*Ir(C2H4)2. Electrophilic Rh and Ir complexes bearing dimethylbutadiene (DMB) ligands have been found to be poor species for C-H activation due to low stability at elevated temperatures. Interestingly, formation of the unique five-coordinate [(DMB)Ir(COE)Cl]2 dimer has been observed. Alkane dehydrogenation using ([superscript dm]Phebox)Ir(OAc)2(OH2) ([superscript dm]Phebox = 2,6-bis(4,4-dimethyloxazolinyl)-3,5-dimethylphenyl) is promoted at 200 °C and results in quantitative formation of olefin and (([superscript dm]Phebox)Ir(OAc)H. At early reaction times 1-octene is the major product, supporting terminal C-H activation by the Ir center. Oxygen can be utilized in this system as a hydrogen acceptor to promote regeneration of the Ir bisacetate species at room temperature. This is the first example of regeneration of a complex for dehydrogenation using oxygen. Unfortunately, the system is not catalytic as the reaction with oxygen is not compatible with the high temperatures required for C-H bond activation. In order to expand the number of examples of alkane dehydrogenation at Ir[superscript III] centers, a second system utilizing the [superscript tBu]NOCON ([superscript tBu]NOCON = 4,6-di-tert-butyl-(1,3-bis(2-pyridyloxy)benzene)) pincer ligand has been developed. Complexes ([superscript tBu] NOCON)M(OAc)2OH2 (M = Rh or Ir) were synthesized and explored for C-H bond functionalization. The Ir analogue promotes alkane dehydrogenation at 200 °C, but is not stable under the reaction conditions. Arene functionalization has also been explored using Ir-aryl complexes. The product of benzene C-H activation, (Phebox)Ir(OAc)Ph has been investigated for arene functionalization using hypervalent iodide reagents and CO. Reactions utilizing C6F5I(TFA)2 are promising and may potentially yield functionalized arene. Coordination of CO to the Ir center has been observed and isomerization of the trans product, ([superscript dm]Phebox)Ir(CO)(OAc)Ph, occurs at room temperature to yield the cis isomer ([superscript dm] Phebox)Ir(OAc)(CO)Ph.

Download or read book Rhodium Mediated Bond Activation written by and published by . This book was released on 2012 with total page 151 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recently, our lab has developed monoanionic tridentate ligand, ToR, showing the corresponding coordination chemistry and catalyst reactivity of magnesium, zirconium, zinc and iridium complexes. This thesis details synthetic chemistry, structural study and catalytic reactivity of the ToR-supported rhodium compounds. Tl[ToR] has been proved to be a superior ligand transfer agent for synthesizing rhodium complexes. The salt metathesis route of Tl[ToM] with [Rh([mu]-Cl)(CO)]2 and [Rh([mu]- Cl)(COE)]2 gives ToMRh(CO)2 (2.2) and ToMRhH([beta]3-C8H13) (3.1) respectively while Tl[ToM] with [Rh([mu]-Cl)(CO)]2 affords ToPRh(CO)2 (2.3). 2.2 reacts with both strong and weak electrophiles, resulting in the oxazoline N-attacked and the metal center-attacked compounds correspondingly. Using one of the metal center-attacked electrophiles, 2.3 was demonstrated to give high diastereoselectivity. Parallel to COE allylic C-H activation complex 3.1, the propene and allylbenzene allylic C-H activation products have also been synthesized. The subsequent functionalization attempts have been examined by treating with Brønsted acids, Lewis acids, electrophiles, nucleophiles, 1,3-dipolar reagents and reagents containing multiple bonds able to be inserted. Various related complexes have been obtained under these conditions, in which one of the azide insertion compounds reductively eliminates to give an allylic functionalization product stoichiometrically. 3.1 reacts with various primary alcohols to give the decarbonylation dihydride complex ToMRh(H)2CO (4.1). 4.1 shows catalytic reactivity for primary alcohol decarbonylation under a photolytic condition. Meanwhile, 2.2 has been found to be more reactive than 4.1 for catalytic alcohol decarbonylation under the same condition. Various complexes and primary alcohols have been investigated as well. The proposed mechanism is based on the stochiometric reactions of the possible metal and organic intermediates. Primary amines, hypothesized to undergo a similar reaction pathway, have been verified to give dehydrogenative coupling product, imines. In the end, the well-developed neutral tridentate Tpm coordinates to the rhodium bis(ethylene) dimer in the presence of TlPF6 to give the cationic complex, [TpmRh(C2H4)2][PF6] (5.1). 5.1 serves as the first example of explicit determination of the solid state hapticity, evidenced by X-ray structure, among all the cationic TpmRM(C2H4)2+ (TpmR = Tpm, Tpm*, M = Rh, Ir) derivatives. The substitution chemistry of this compound has been studied by treating with soft and hard donors. The trimethylphosphine-sbustituted complex activates molecular hydrogen to give the dihydride compound.

Download or read book Rhodium and Iridium Complexes Supported by Chelating Bis N heterocyclic Carbene Ligands written by Roxy Joanne Lowry and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: ABSTRACT: Eighty-five percent of all industrial chemical processes occur catalytically. The world's expanding appetite for mass production of exotic chemicals necessitates the design and application of enhanced catalysts. To optimize catalytic materials, the detailed relationships between catalyst architecture and reactivity must be determined. Although for many ligand families these relationships are well understood, novel catalysts require in depth empirical investigation to determine these connections. The design of a novel di-N-heterocyclic carbene family of ligands in reported herein. These C2 symmetric ligands are based on the rigid 9,10-dihydro-9,10-ethanoanthracene backbone and designed for utilization in chiral catalysis. Thorough investigation into the relationships between the ligand's structure and the architecture of the resulting rhodium and iridium catalysts directed the design of three generations of our novel ligand family. The first generation, trans-1,1'-[9,10-dihydro-9,10-ethanoanthracene-11,12- diyldimethanediyl]bis(benzylimidazole) bis(triflouromethansulfonate) [DEAM-BI](OTf)2 (2-1), is too flexible to enforce a rigid chiral pocket about a metal center under catalytic conditions. The constrained second generation ligands, trans-1,1'-(9,10-dihydro-9,10-ethanoanthracene.

Download or read book Therapeutic Rhodium Complexes written by Afzal Hussain and published by Springer Nature. This book was released on 2023-06-29 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book describes the emergence and recent advances in the design and development of rhodium complexes as therapeutic agents. Different classes of anticancer rhodium complexes with particular emphasis on ligands containing nitrogen-oxygen donor atoms are presented. Anticancer rhodium complexes of N-heterocyclic carbenes are described, while half-sandwich, heterobimetallic, and multinuclear rhodium complexes are discussed. Therapeutic applications of rhodium complexes beyond cancer such as antibacterial agents or antiviral agents are also analyzed, among others. Their mechanism of action is overviewed in detail, and the authors thoroughly comment on the challenges and future outlooks of research in the development of rhodium metallodrugs. This title highlights the important research carried out in the development of therapeutic rhodium complexes and is of great interest to graduates and researchers working in the area of rhodium-based therapeutic drugs.

Download or read book Synthesis and Reactions of Complexes of Rhodium and Iridium Having Chelating N O donor Ligands written by Namadzavho Enos Sitabule and published by . This book was released on 2000 with total page 302 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Synthesis and Reactivity of Rhodium and Iridium Silyl and Silylene Complexes Supported by PNP Pincer Ligands written by Elisa E. Calimano and published by . This book was released on 2009 with total page 552 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Iridium I Complexes for the Functionalisation of Carbon hydrogen Bonds written by Renan Zorzatto and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The development of catalytic systems for the functionalisation of carbon-hydrogen bonds has been an intensive area of research for the last 5 decades. In this context, transition metal complexes play a crucial role in reaction discovery, mechanistic evaluation and synthetic applications. In the Kerr group, this technology has been explored in the context of hydrogen isotope exchange, resulting in the development of highly active iridium(I) complexes bearing phosphines and NHC ligands. Despite their broad functional group compatibility, existing methods for isotope exchange are ineffective in the labelling of sterically encumbered directing groups. Hence, in the first chapter we investigate the synthesis of three new iridium(I) complexes bearing chelating phosphine-functionalised NHC ligands, and their application in the isotope exchange of sterically hindered carbamates. Our initial studies revealed high catalytic efficiency and tolerance for steric encumbrance, prompting us to perform a combined theoretical and experimental investigation of the reaction mechanism.Therefore, by conducting DFT calculations and kinetic experiments, we were able to identify a rich dynamic behaviour in solution and ultimately propose a reaction mechanism. Additionally, our interest in the activation of carbon-hydrogen bonds resulted in the exploration of a theoretical model for the prediction of enthalpies of activation, resulting in the identification of relevant electronic and steric descriptors.From the knowledge gathered in our initial studies, the second chapter describes the application of our novel iridium catalysts in the functionalisation of carbon-hydrogen bonds in the context of hydroarylation of olefins. Thus, we identified carboxylic acids as suitable directing groups for this transformation and employed Design of Experiments to optimise the reaction conditions. Synthetic studies were focused on the preparation of 14 substrates, enabling quick assessment of the capabilities and limitations of this reaction. These investigations resulted in a synthetic method suitable for the synthesis of bi- and tricycles featuring tertiary and quaternary benzylic stereocentres in a racemic fashion.Finally, we investigated the mechanism of this process by DFT calculations, which led us to identify a plausible reaction pathway which should guide future kinetic evaluations.

Download or read book Rhodium Catalyzed Hydroformylation written by Piet W.N.M. van Leeuwen and published by Springer Science & Business Media. This book was released on 2006-04-11 with total page 291 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the last decade there have been numerous advances in the area of rhodium-catalyzed hydroformylation, such as highly selective catalysts of industrial importance, new insights into mechanisms of the reaction, very selective asymmetric catalysts, in situ characterization and application to organic synthesis. The views on hydroformylation which still prevail in the current textbooks have become obsolete in several respects. Therefore, it was felt timely to collect these advances in a book. The book contains a series of chapters discussing several rhodium systems arranged according to ligand type, including asymmetric ligands, a chapter on applications in organic chemistry, a chapter on modern processes and separations, and a chapter on catalyst preparation and laboratory techniques. This book concentrates on highlights, rather than a concise review mentioning all articles in just one line. The book aims at an audience of advanced students, experts in the field, and scientists from related fields. The didactic approach also makes it useful as a guide for an advanced course.

Download or read book Rhodium and Iridium Pincer Complexes Supported by Bis phosphino silyl Ligation written by Erin Morgan 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 Activation and Functionalization of C H Bonds written by Karen I. Goldberg and published by ACS Symposium. This book was released on 2004 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Activation and Functionalization of C-H Bonds explores recent developments in the reaction chemistry of solution-phase transition-metal based systems with simple hydrocarbons and with more complex organic molecules. More than 20 internationally leading research groups contributed to this volume, and their chapters cover such topics as fundamental theoretical and mechanistic studies of C-H bond activation by metal complexes, catalytic systems for alkane functionalization, and new applications in synthetic organic chemistry. An introductory chapter offers an overview of stoichiometric and catalytic reactions of C-H bonds with transition metal complexes. The C-H bond is the most widespread linkage in organic chemistry, present in virtually every organic molecule. Unfortunately, C-H bonds are famously resistant to selective chemical transformations. The development of methods for their selective transformations has enormous potential value in fields ranging from the chemistry of fuels (for example, the conversion of methane to methanol) to the synthesis of the most complex organic molecules.

Download or read book Rhodium Catalysis in Organic Synthesis written by Ken Tanaka and published by John Wiley & Sons. This book was released on 2018-12-28 with total page 254 pages. Available in PDF, EPUB and Kindle. Book excerpt: An essential reference to the highly effective reactions applied to modern organic synthesis Rhodium complexes are one of the most important transition metals for organic synthesis due to their ability to catalyze a variety of useful transformations. Rhodium Catalysis in Organic Synthesis explores the most recent progress and new developments in the field of catalytic cyclization reactions using rhodium(I) complexes and catalytic carbon-hydrogen bond activation reactions using rhodium(II) and rhodium(III) complexes. Edited by a noted expert in the field with contributions from a panel of leading international scientists, Rhodium Catalysis in Organic Synthesis presents the essential information in one comprehensive volume. Designed to be an accessible resource, the book is arranged by different reaction types. All the chapters provide insight into each transformation and include information on the history, selectivity, scope, mechanism, and application. In addition, the chapters offer a summary and outlook of each transformation. This important resource: -Offers a comprehensive review of how rhodium complexes catalyze a variety of highly useful reactions for organic synthesis (e.g. coupling reactions, CH-bond functionalization, hydroformylation, cyclization reactions and others) -Includes information on the most recent developments that contain a range of new, efficient, elegant, reliable and useful reactions -Presents a volume edited by one of the international leading scientists working in the field today -Contains the information that can be applied by researchers in academia and also professionals in pharmaceutical, agrochemical and fine chemical companies Written for academics and synthetic chemists working with organometallics, Rhodium Catalysis in Organic Synthesis contains the most recent information available on the developments and applications in the field of catalytic cyclization reactions using rhodium complexes.

Download or read book Synthetic and Mechanistic Studies of Carbon hydrogen Bond Activation by Iridium III Complexes and Development of a Transition Metal Catalyzed Alkene Aziridination Reaction written by Peter James Alaimo and published by . This book was released on 1999 with total page 556 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Development and Study of New Chelating Ligands with Combinations of Pyridinylidene Amide PYA and Remote NHC Donors as Supporting Ligands for Homogeneous Metal Catalysts written by Bikimi Ayiya and published by . This book was released on 2019 with total page 279 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis describes the design and syntheses of metal complexes that contain chelating ligands with different combinations of pyridinylidene amide (PYA), amidate, and remote-N-heterocyclic carbene (rNHC) or a mesoionic-remote-N-heterocyclic carbene (m-rNHC) donor functions. Although ligands with amidate donors are relatively well known, metal complexes of ligands containing the other donors are relatively unexplored. All these groups exhibit strong donating properties. It was expected that suitable metal complexes of these new ligands could show interesting catalytic activity in reactions such as transfer hydrogenation. In Chapter 1, an overview of the chemistry and existing synthetic routes to a range of different pyridine derived ligands are given. The coordination chemistry and applications of these classes of ligands are briefly discussed and the motivation for this work is outlined at the end. In Chapter 2, the syntheses of two new palladium(II) NC’N-tridentate pincer complexes ([Pd(L)(LPPy{Me}3)]OTf), L= Cl, OAc) that features both rNHC and two PYA donors are described. The tricationic pro-ligand [H2LPPy{Me}3][OTf]3, bearing two pendant alkylated 4-pyridyl arms at the 3,5-positions of the head group pyridine was metallated with Pd(OAc)2 or [PdCl2(PhCN)2] by heating with NaOAc in situ. The two complexes were stable in air and moisture, but sparingly soluble in common solvents and this precluded further studies. The smaller related bidentate pro-ligands [LmPy{Me}2]OTf and [LPPy{Me}2]OTf, were synthesised and on metallation by heating in the presence of acetate afforded [RhCl(LmPy{Me}2)Cp*]OTf and [RhCl(LPPy{Me}2)Cp*]OTf. X-ray crystallography and NMR studies of these complexes confirmed coordination occurred through PYA and rNHC donors. In Chapters 3 and 4, the syntheses of the sets of pro-ligands [HLp1-6{Bz}]Cl and [HLm1-6{Bz}]Clis described. The compounds within each set differ in that they have different substituents (e.g. Ph, Me, OMe, Naphthyl, Cl and NO2) in the para-position of the aryl ring attached to the insipient amidate nitrogen donor. On metallation, these pro-ligands coordinate as bidentate ligands with amidate and rNHC donors (in the case of [HLm1-6{Bz}]Cl) or amidate and m-rNHC donors (in the case of [HLp1-6{Bz}]Cl). Metallation of the pro-ligands using [IrCp*Cl2]2as the metal substrate gives the sets of neutral complexes [IrCl(Lm1-6{Bz})Cp*] and [IrCl(Lp1-6{Bz})Cp*]. The corresponding cationic complexes [Ir(Lx1-6{Bz})(L)Cp*]OTf(L= DMSO, CO, Py, x= m, p) were prepared by Ag+ promoted exchange of the chloride ligands in [IrCl(Lx1-6{Bz})Cp*] (x= m, p) with DMSO, CO or pyridine. Comparison of the molecular structures of both the neutral and cationic forms of all the complexes obtained via single-crystal XRD suggests that the complexes with the rNHC donors ([IrCl(Lm1-6{Bz})Cp*], [Ir(Lm1-6{Bz})(L)Cp*]OTf(L= DMSO, CO, Py) all exhibit a similar pattern of C–C bond lengths within the pyridinium ring of the rNHC donor with some 2,5-diene character. In contrast, the complexes with m-rNHC donors ([IrCl(Lp1-6{Bz})Cp*], [Ir(Lp1-6{Bz})(L)Cp*]OTf(L= DMSO, CO) the C–C bond lengths in the corresponding rings are nearly equal suggesting a more pronounced aromatic character in these cases. On treatment of the pro-ligands [HLm1-2{Bz}]Cl with RuCl3.xH2Othe complexes [RuCl(Lm2,3{Bz})(PPh3)2(CO)]Cl were obtained. Unlike the iridium complexes formed with the same pro-ligands, the donor groups in these complexes were the carbon of a rNHC and the oxygen of the unchanged carboxamide group. The catalytic activities of the complexes [Ir(Lx1-6{Bz})(L)Cp*]OTf(L = DMSO, x= m,p) and [RuCl(Lm2,3{Bz})(PPh3)2(CO)]Cl were tested in both transfer hydrogenation and dehydrogenation. The results of these studies are described in Chapter 5. Notably, it was found that the iridium mesoionic-rNHC-containing complexes with methoxy substituents were the most active in the dehydrogenation of benzyl alcohol to benzaldehyde, achieving 99.9% conversion under 12 h. In transfer hydrogenation using isopropanol as the hydrogen source, the same mesoionic-rNHC-containing iridium complexes with OMe substituents were also the best iridium catalysts. Complete conversion of benzaldehyde to benzyl alcohol with 2 mol% catalyst loading occurred in 8 min. However, the ruthenium complexes displayed exceptionally good transfer hydrogenation catalytic activity reaching 99.9% conversion within3 min at 1 mol% catalyst loading, with TOF 1700 h-1. It was proposed that the hemilabilenature of the O-bound carboxamide group, the ancillary ligands and trans-influence alongside the donor strength of the rNHC group were important factors for the high activity displayed by the Ru(II) complexes. Finally, the thesis conclusion is outlined in this chapter.

Download or read book Bifunctional Rhodium and Iridium Platforms Towards C H Activation written by Travis John Morrow and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Pendent nucleophiles are essential partners in the cleavage and formation of bonds with hydrogen (e.g. protonation/deprotonation), but binding of the pendent group to the metal and the potential trapping of complexes in inactive states are a significant problem. The dipyridylmethane-based ligand framework bis(2-pyridyl)-N-pyrrolidinomethane([superscript]R,pyrCPy2), bearing a hemilabile pyrrolidine moiety, has been synthesized and complexes of the type [([superscript]R,pyrCPy2)M(COD)]X (COD = 1,5-cyclooctadiene) were prepared. The solution-phase ligand dynamics and relative protonation preferences were investigated via1H NMR spectroscopy; although favorable, pendent amine binding does not kinetically inhibit pendent base protonation. Protonation at the metal (with concomitant pyrrolidine binding) has been found to be favorable for Ir, whereas N-protonation is favorable for Rh. DFT calculations predict that the RhIII hydrides have much higher relative acidities than their Ir congeners (∆pK[subscript]a ≃ 7–8 in CH2Cl2), and are also more acidic than the strong acid[H(OEt2)2][B(C6F5)4]. The second part of this dissertation examines oxidative addition of carbon-halogen bonds at transition metals, which typically follow either a two-electron pathway (concerted MR/M-X formation) or a radical chain pathway (stepwise M-R/M-X formation). When the reactive metal species is generated slowly, however, both mechanisms can compete to yield unexpected reactivity paths. The present report highlights the synthesis of rhodiummethylidenes from chloroalkanes (e.g. CH2Cl2 and CHCl3) at POP-pincer frameworks(e.g. POP = 4,6-bis(di-tert-butylphosphino)dibenzo[b,d]furan) via a cascade of halide abstraction and electron transfer steps. Experimental and computational studies are covered that support our proposed mechanism, including characterization of important reaction intermediates. The overall transformation presented represents a route towards reactive metal alkylidenes using milder and less-reactive carbenoid precursors than what is presently used.

Download or read book Organometallic complexes of Rhodium Iridium and Platinum written by Ingrid C. M. Wehman-Ooyevaar and published by . This book was released on 1992 with total page 183 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Rhodium III and Iridium III Complexes Bearing Chelating C pNHC phosphine Or C pNHC C NHC Ligands Synthesis and Catalytic Applications written by Francisco Aznárez Pemán and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: