N-heterocyclic Silyl and Silylene Metal Complexes Within a PSIP Framework

N-heterocyclic Silyl and Silylene Metal Complexes Within a PSIP Framework
Author: Amy Marie Jehl
Publisher:
Total Pages: 237
Release: 2019
Genre: Carbon dioxide
ISBN: 9781085729345
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N-heterocyclic carbenes (NHC) are strong Lewis bases that have demonstrated broad utility as ligands for transition metal (TM) catalysts. Silicon analogues, N-heterocyclic silylenes (NHSi), are comparatively less well studied. The decreased [Pi]-[pi] overlap between the Si 3p orbital and adjacent nitrogen lone pairs creates a more accessible vacant orbital on Si, resulting in increased ambiphilic character. When bound to a transition metal, this empty orbital presents an opportunity to cooperatively bind and activate substrate molecules. To increase the stability of a potential metal-silylene complex we targeted the diphosphine ligand precursor 1,2-bis(R2PCH2NCH2)C6H4 (R = alkyl or aryl), first reported by Yamashita and Nozaki in the construction of a boron-anchored pincer. Reported here are (PCy)2Si pincer ligands and their TM-silylene complexes for small molecule activation.

Synthesis and Catalytic Application of PSiP- and P,N-Ligated Complexes of First-Row Metals

Synthesis and Catalytic Application of PSiP- and P,N-Ligated Complexes of First-Row Metals
Author: Luke Murphy
Publisher:
Total Pages: 0
Release: 2020
Genre:
ISBN:
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The study of PSiP pincer complexes of second- and third-row transition metals has led to the discovery of challenging bond activation chemistry as well as catalytic chemistry. While there now exists a considerable amount of literature regarding the behavior of PSiP complexes of the second- and third-row metals, comparatively little is known of the behavior of these ligands with the first-row metals. There has been a recent push toward the study of first-row transition metal chemistry in general, due to their high natural abundance and often lower toxicity when compared to their second- and third-row congeners. This document details progress toward the synthesis of a variety of novel Fe, Co and Ni complexes featuring PSiP ligation and application toward catalytic reduction of unsaturated substrates. In terms of (PSiP)Fe chemistry, considerable progress has been made toward the synthesis of novel coordination complexes, in particular the synthesis of hydride complexes of Fe. Organometallic hydride complexes are often implicated as important catalytic intermediates, and in this case a bis(dinitrogen) adduct of an Fe hydride has been identified as a highly active catalyst for the hydrogenation of olefins. Co chemistry with the same ligand has unveiled intriguing examples of both H2 and O2 bond cleavage chemistry, and again has led to an example of an alkene hydrogenation catalyst. A novel PSiP framework has been developed and applied toward chemistry of the group 10 transition metals, particularly nickel. In this regard, chemistry of complexes supported by this new ligand was found to be markedly different than that of similar complexes supported by the previous iteration of the ligand. In particular, a Ni hydride complex was successfully prepared and applied toward the selective reduction of CO2 to the formaldehyde level via hydroboration. Lastly, outside the realm of PSiP chemistry, a new monoanionic P,N-based ligand has been developed and its chemistry has been explored with respect to Fe and Co. Interesting coordination chemistry has been observed with this new ligand, and examples of reactive Fe and Co complexes have been obtained and applied toward the challenging reduction of tertiary amides to amines via catalytic hydrosilylation.

Syntheses and Reactivity Studies of Transition Metal Complexes Featuring Metal - Main Group Multiple Bonds

Syntheses and Reactivity Studies of Transition Metal Complexes Featuring Metal - Main Group Multiple Bonds
Author: Meg E. Fasulo
Publisher:
Total Pages: 120
Release: 2012
Genre:
ISBN:
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The ruthenium triflate complex Cp*(PiPr3)RuOTf (1) was generated from the reaction of Cp*(PiPr3)RuCl with Me3SiOTf in dibutyl ether. Complex 1 reacted with primary and secondary silanes to produce a family of Ru(IV) silyl dihydride complexes of the type Cp*(PiPr3)Ru(H)2(SiRR'OTf) (3 - 12). Structural analyses of complexes 8 (R = R' = Ph) and 12 (R = R' = fluorenyl) revealed the presence of a tetrahedral silicon center and a four-legged piano stool geometry about ruthenium. Anion abstraction from Cp*(PiPr3)Ru(H)2(SiHROTf) by [Et3Si*toluene][B(C6F5)4] afforded hydrogen-substituted cationic ruthenium silylene complexes [Cp*(PiPr3)Ru(H)2(=SiHR)][B(C6F5)4] (R = Mes (13), R = Si(SiMe3) (14)) that display a significant Ru - H ... Si interaction, as indicated by relatively large 2JSiH coupling constants (2JSiH = 58.2 Hz (13), 2JSiH = 37.1 Hz (14)). The syntheses of secondary silylene complexes [Cp*(PiPr3)Ru(H)2(=SiRR')][B(C6F5)4] (R = R' = Ph (15); R = Ph, R' = Me (16), R = R' = fluorenyl (17)) were also achieved by anion abstraction with [Et3Si*toluene][B(C6F5)4]. Complexes 15 - 17 do not display strong Ru - H ... Si secondary interactions, as indicated by very small 2JSiH coupling constant values. The cationic ruthenium silylene complex [Cp*(PiPr3)Ru(H)2(SiHMes)] [CB11H6Br6], a catalyst for olefin hydrosilations with primary silanes, was isolated and characterized by X-ray crystallography. Relatively strong interactions between the silylene Si atom and Ru-H hydride ligands appear to reflect a highly electrophilic silicon center. Kinetic and mechanistic studies on hydrosilations with this catalyst reveal a fast, initial addition of the Si-H bond of the silylene complex to the olefin. Subsequent migration of a hydride ligand to silicon produces a 16-electron intermediate, which can be trapped by olefin, resulting in inhibition of catalysis, or intercepted by the silane substrate. The latter reaction pathway, involving oxidative addition of the Si-H bond and a somewhat concomitant loss of product, is the rate-determining step in the catalytic cycle. Reactions of the cationic ruthenium silylene complexes [Cp*(PiPr3)Ru(H)2(=SiRR')][B(C6F5)4] (R = Mes, R' = H, 1; R = R' =Ph, 2) with alkenes, alkynes, ketones, and Lewis bases were explored. Addition of 1-hexene, 3,3-dimethylbut-1-ene, styrene, and cyclopentene to 1 afforded the disubstituted silylene products [Cp*(PiPr3)Ru(H)2(=SiMesR)][B(C6F5)4] (R = Hex, 3; R = CH2CH2tBu, 4; R = CH2CH2Ph, 5; R = C5H9, 6). Analogous reactions with 2-butyne and 3,3-dimethylbut-1-yne yielded the vinyl-substituted silylene complexes [Cp*(PiPr3)Ru(H)2(=Si(CR=CHR')Mes)][B(C6F)4] (R = R' = Me, 7; R = H, R' = tBu, 8). Complex 1 undergoes reactions with ketones to give the heteroatom-substituted silylene complexes [Cp*(PiPr3)Ru(H)2(=Si(OCHPhR)Mes)][B(C6F)4] (R = Ph, 9; R = Me, 10). Interestingly, complexes 3 - 8 display a weak interaction between the hydride ligands and the silicon center, while 9 and 10 exhibit a relatively large interaction (as determined by 2JSiH values). The reaction of isocyanates with 1 resulted in the silyl complexes [Cp*(PiPr3)Ru(H)2(Si(Mes)[n2-O(CH)(NC6H4R)][B(C6F5)4] (R = H, 11; R = CF3, 12), and an intermediate in this transformation is observed. Complex 2 was subjected to various Lewis bases to yield the base-stabilized silylene complexes [Cp*(PiPr3)Ru(H)2(SiPh2*L)][B(C6F)4] (L = DMAP, 13; L = Ph2CO, 14; L = PhCONH2, 15; L = NHMePh, 16, L = tBuSONH2, 18) and the reaction of 1 with NHMePh gave [Cp*(PiPr3)Ru(H)2(SiHMes*NHMePh)][B(C6F)4]. The cationic germylene complex [Cp*(PiPr3)Ru(H)2(=GeMes2)][OTf] (1) was synthesized from the reaction of Cp*(PiPr3)RuOTf with H2GeMes2, and addition of DMAP to 1 yielded the neutral germylene complex [Cp*(PiPr3)Ru(H)(=GeMes2) (2). The reaction of H3GeTrip and Cp*(PiPr3)RuCl gave the germyl complex Cp*(PiPr3)Ru(H)2(GeHTripCl) (3), which undergoes a reaction with Li(Et2O)2[B(C6F5)4] to afford the cationic H-substituted germylene complex [Cp*(PiPr3)Ru(H)2(=GeHTrip)][B(C6F5)4] (4). Addition of 1-hexene, 3,3-dimethylbut-1-ene, styrene, and allyl chloride to 4 afforded the disubstituted germylene products [Cp*(PiPr3)Ru(H)2(=GeTripR)][B(C6F5)4] (R = Hex, 5; R = CH2CH2Ph, 6; R = CH2CH2tBu, 7; R = CH2CH2CH2Cl, 8). Analogous reactions with 2-butyne and 3,3-dimethylbut-1-yne yielded the vinyl-substituted germylene complexes [Cp*(PiPr3)Ru(H)2(=Ge(CR=CHR')Trip)][B(C6F)4] (R = H, R' = tBu, 9; R = R' = Me, 10). New di(phosphine)-supported rhodium and iridium silyl complexes were synthesized. Reactions of the di(t-butylphosphino)ethane complex (dtbpe)Rh(CH2Ph) with Ph2SiH2 and Et2SiH2 resulted in isolation of (dtbpe)Rh(H)2(SiBnPh2) (1, Bn = CH2Ph) and (dtbpe)Rh(H)2(SiBnEt2) (2), respectively. Both 1 and 2 display strong interactions between the rhodium hydride ligands and the silyl ligand, as indicated by large 2JSiH values (44.4 and 52.1 Hz). The reaction of (dtbpm)Rh(CH2Ph) (dtbpm = di(t-butylphosphino)methane) with Mes2SiH2 gave the pseudo-three-coordinate Rh complex (dtbpm)Rh(SiHMes2) (3), which is stabilized in the solid state by agostic interactions between the rhodium center and two C - H bonds of a methyl substituent of a mesityl group. The analogous germanium compound (dtbpm)Rh(GeHMes2) (4) is also accessible. Complex 3 readily undergoes reactions with diphenylacetylene, phenylacetylene, and 2-butyne to give the silaallyl complexes (dtbpm)Rh[Si(CPh=CHPh)Mes2] (5), (dtbpm)Rh[Si(CH=CHPh)Mes2] (7), and (dtbpm)Rh(Si(CMe=CHMe)Mes2) (8) via net insertions into the Si - H bond. The germaallyl complexes (dtbpm)Rh[Ge(CPh=CHPh)Mes2] (6) and (dtbpm)Rh[Ge(CMe=CHMe)Mes2] (9) were synthesized under identical conditions starting from 4. The reaction of (dtbpm)Rh(CH2Ph) with 1 equiv of TripPhSiH2 yielded (dtbpm)Rh(H)2[5,7-diisopropyl-3-methyl-1-phenyl-2,3-dihydro-1H-silaindenyl-kSi] (11), and catalytic investigations indicate that both (dtbpm)Rh(CH2Ph) and 11 are competent catalysts for the conversion of TripPhSiH2 to 5,7-diisopropyl-3-methyl-1-phenyl-2,3-dihydro-1H-silaindole. A dtbpm-supported Ir complex, [(dtbpm)IrCl]€2, was used to access the dinuclear bridging silylene complexes [(dtbpm)IrH](SiPh2)(Cl)2[(dtbpm)IrH] (12) and [(dtbpm)IrH](SiMesCl)( -Cl)(H)[(dtbpm)IrH] (13). The reaction of [(dtbpm)IrCl]2 with a sterically bulky primary silane, (dmp)SiH3 (dmp = 2,6-dimesitylphenyl), allowed isolation of the mononuclear complex (dtbpm)Ir(H)4(10-chloro-1-mesityl-5,7-dimethyl-9,10-dihydrosilaphenanthrene-Si) (14), in which the dmp substituent has undergone C-H activation. The dichloride complex Cp*(Am)WCl2 (1, Am = [(iPrN)2CMe]- ) reacted with the primary silanes PhSiH3, (p-tolyl)SiH3, (3,5-xylyl)SiH3, and (C6F5)SiH3 to produce the W(VI) (silyl)trihydrides Cp*(Am)W(H)3(SiHPhCl) (2), Cp*(Am)W(H)3(SiHTolylCl) (3), Cp*(Am)W(H)3(SiHXylylCl) (4), and Cp*(Am)W(H)3[SiH(C6F5)Cl] (5). In an analogous manner, 1 reacted with PhSiH2Cl to give Cp*(Am)W(H)3(SiPhCl2) (6). Complex 6 can alternatively be quantitatively produced from the reaction of 2 with Ph3CCl. NMR spectroscopic studies and X-ray crystallography reveal an interligand H ... Si interaction between one W - H and the chlorosilyl group, which is further supported by DFT calculations. Complexes of Ru(II) containing the pincer ligand [-N(2-PPh2-4-Me-C6H3)2] (PNPPh) were prepared. The complex (PNPPhH)RuCl2 (1) was treated with 2 equiv AgOTf to produce the triflate complex (PNPPhH)Ru(OTf)2 (2). Complex 1 was also treated with an excess of NaBH4 to give a bimetallic complex [(PNPPh)RuH3]2 (3). A number of methods, including X-ray crystallography, NMR spectroscopy, and computational studies, were used to probe the structure of 3. Addition of Lewis bases to 3 resulted in octahedral complexes containing a hydride ligand trans to a dihydrogen ligand.

The Chemistry of Pincer Compounds

The Chemistry of Pincer Compounds
Author: David Morales-Morales
Publisher: Elsevier
Total Pages: 467
Release: 2011-08-11
Genre: Science
ISBN: 0080545157
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Pincer complexes are formed by the binding of a chemical structure to a metal atom with at least one carbon-metal bond. Usually the metal atom has three bonds to a chemical backbone, enclosing the atom like a pincer. The resulting structure protects the metal atom and gives it unique properties.The last decade has witnessed the continuous growth in the development of pincer complexes. These species have passed from being curiosity compounds to chemical chameleons able to perform a wide variety of applications. Their unique metal bound structures provide some of the most active catalysts yet known for organic transformations involving the activation of bonds. The Chemistry of Pincer Compounds details use of pincer compounds including homogeneous catalysis, enantioselective organic transformations, the activation of strong bonds, the biological importance of pincer compounds as potential therapeutic or pharmaceutical agents, dendrimeric and supported materials. * Describes the chemistry and applications of this important class of organometallic and coordination compounds* Covers the areas in which pincer complexes have had an impact* Includes information on more recent and interesting pincer compounds not just those that are well-known

Non-Noble Metal Catalysis

Non-Noble Metal Catalysis
Author: Robertus J. M. Klein Gebbink
Publisher: John Wiley & Sons
Total Pages: 610
Release: 2019-04-29
Genre: Technology & Engineering
ISBN: 3527340610
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An expert overview of current research, applications, and economic and environmental advantages The study and development of new homogeneous catalysts based on first-row metals (Mn, Fe, Co, Ni, and Cu) has grown significantly due to the economic and environmental advantages that non-noble metals present. Base metals offer reduced cost, greater supply, and lower toxicity levels than noble metals?enabling greater opportunity for scientific investigation and increased development of practical applications. Non-Noble Metal Catalysis provides an authoritative survey of the field, from fundamental concepts and computational methods to industrial applications and reaction classes. Recognized experts in organometallic chemistry and homogeneous catalysis, the authors present a comprehensive overview of the conceptual and practical aspects of non-noble metal catalysts. Examination of topics including non-innocent ligands, proton-coupled electron transfer, and multi-nuclear complexes provide essential background information, while areas such as kinetic lability and lifetimes of intermediates reflect current research and shifting trends in the field. This timely book demonstrates the efficacy of base metal catalysts in the pharmaceutical, fine-chemical, and agrochemical industries, addressing both environmental and economic concerns. Providing essential conceptual and practical exploration, this valuable resource: -Illustrates how unravelling new reactivity patterns can lead to new catalysts and new applications -Highlights the multiple advantages of using non-noble metals in homogenous catalysis -Demonstrates how the availability of non-noble metal catalysis reduces costs and leads to immense savings for the chemical industry -Reveals how non-noble metal catalysis are more sustainable than noble metals such as palladium or platinum Non-Noble Metal Catalysis: Molecular Approaches and Reactions is an indispensable source of up-to-date information for catalytic chemists, organic chemists, industrial chemists, organometallic chemists, and those seeking to broaden their knowledge of catalytic chemistry.

Frustrated Lewis Pairs I

Frustrated Lewis Pairs I
Author: Gerhard Erker
Publisher: Springer
Total Pages: 354
Release: 2014-07-08
Genre: Science
ISBN: 364236697X
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Discovery of Frustrated Lewis Pairs: Intermolecular FLPs for Activation of Small Molecules, by Douglas W. Stephan Intramolecular Frustrated Lewis Pairs: Formation and Chemical Features, by Gerald Kehr, Sina Schwendemann, Gerhard Erker Frustrated Lewis Pair Mediated Hydrogenations, by Douglas W. Stephan, Gerhard Erker Amine-Borane Mediated Metal-Free Hydrogen Activation and Catalytic Hydrogenation, by Victor Sumerin, Konstantin Chernichenko, Felix Schulz, Markku Leskelä, Bernhard Rieger, Timo Repo Hydrogen Activation by Frustrated Lewis Pairs: Insights from Computational Studies, by Tibor András Rokob, Imre Pápai Quantum Chemistry of FLPs and Their Activation of Small Molecules: Methodological Aspects, by Birgitta Schirmer, Stefan Grimme Computational Design of Metal-Free Molecules for Activation of Small Molecules, Hydrogenation, and Hydroamination, by Zhi-Xiang Wang, Lili Zhao, Gang Lu, Haixia Li, Fang Huang Computational Studies of Lewis Acidity and Basicity in Frustrated Lewis Pairs, by Thomas M. Gilbert Solid-State NMR as a Spectroscopic Tool for Characterizing Phosphane - Borane Frustrated Lewis Pairs, by Thomas Wiegand, Hellmut Eckert, Stefan Grimme

Pincer Compounds

Pincer Compounds
Author: David Morales-Morales
Publisher: Elsevier
Total Pages: 756
Release: 2018-04-11
Genre: Science
ISBN: 0128129328
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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

Cobalt Catalysis in Organic Synthesis

Cobalt Catalysis in Organic Synthesis
Author: Marko Hapke
Publisher: John Wiley & Sons
Total Pages: 480
Release: 2020-04-06
Genre: Technology & Engineering
ISBN: 3527344500
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Provides a much-needed account of the formidable "cobalt rush" in organic synthesis and catalysis Over the past few decades, cobalt has turned into one of the most promising metals for use in catalytic reactions, with important applications in the efficient and selective synthesis of natural products, pharmaceuticals, and new materials. Cobalt Catalysis in Organic Synthesis: Methods and Reactions provides a unique overview of cobalt-catalysed and -mediated reactions applied in modern organic synthesis. It covers a broad range of homogeneous reactions, like cobalt-catalysed hydrogenation, hydrofunctionalization, cycloaddition reactions, C-H functionalization, as well as radical and biomimetic reactions. First comprehensive book on this rapidly evolving research area Covers a broad range of homogeneous reactions, such as C-H activation, cross-coupling, synthesis of heterocyclic compounds (Pauson-Khand), and more Chapters on low-valent cobalt complexes as catalysts in coupling reactions, and enantioselective cobalt-catalyzed transformations are also included Can be used as a supplementary reader in courses of advanced organic synthesis and organometallic chemistry Cobalt Catalysis in Organic Synthesis is an ideal book for graduates and researchers in academia and industry working in the field of synthetic organic chemistry, catalysis, organometallic chemistry, and natural product synthesis.

Activation of Small Molecules

Activation of Small Molecules
Author: William B. Tolman
Publisher: John Wiley & Sons
Total Pages: 382
Release: 2006-12-13
Genre: Science
ISBN: 3527609377
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The first to combine both the bioinorganic and the organometallic view, this handbook provides all the necessary knowledge in one convenient volume. Alongside a look at CO2 and N2 reduction, the authors discuss O2, NO and N2O binding and reduction, activation of H2 and the oxidation catalysis of O2. Edited by the highly renowned William Tolman, who has won several awards for his research in the field.