Reactivity and Intramolecular Migration Chemistry of Transition-metal Silylene Complexes PDF Download
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Author: Gregory Paul Mitchell
Publisher:
ISBN:
Category :
Languages : en
Pages : 340
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Author: Gregory Paul Mitchell
Publisher:
ISBN:
Category :
Languages : en
Pages : 340
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Author: Meg E. Fasulo
Publisher:
ISBN:
Category :
Languages : en
Pages : 120
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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.
Author: Louis S. Hegedus
Publisher: University Science Books
ISBN: 9781891389047
Category : Science
Languages : en
Pages : 358
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This second edition offers easy access to the field of organotransition metal chemistry. The book covers the basics of transition metal chemistry, giving a practical introduction to organotransition reaction mechanisms.
Author: Eva Neumann
Publisher: Cuvillier Verlag
ISBN: 3736918011
Category : Science
Languages : en
Pages : 244
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The term ligand [latin, ligare = bind] has its origin in coordination chemistry. It denotes a molecule that is able to bind to a metal center in most cases via one or several free electron pairs.[1] Ligands can be described by the number of electron-pair donor atoms as monodentate, bidentate, tridentate etc. ligands. The latter are also called chelating ligands [greek, chele = (crab’s) claw]. A typical classification of ligands is according to their electronic properties. They serve either as a σ-donating, σ-donating/π-accepting, or σ,π-donating/π-accepting ligands.[2] A more practical, often encountered approach is the classification of ligands according to their donor atoms, especially when larger molecules and molecules containing heteroatoms are regarded (compare 1.2). Coordination chemistry was already established in the 19th century. In 1893 Alfred Werner suggested an octahedral arrangement of ligands coordinated to a central metal ion for many compounds. This explained, for example, the appearance and reactivity of four different cobalt(III) complexes (Figure 1.1), when CoCl2 is dissolved in aqueous ammonia and then oxidized by air to the +3 oxidation state. The formulas of these complexes can be written as depicted in Figure 1.1. Werner’s work was rewarded with the Nobel prize in 1913.[3]
Author: Ralph G. Wilkins
Publisher: Wiley-VCH
ISBN: 9783527282531
Category : Science
Languages : en
Pages : 480
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Book Description
This thoroughly revised and updated edition of one of the classics of kinetics text books continues the successful concept of the 1974 edition: In its first part, a simplified approach to the determination of rate laws and mechnisms is given steadily working up to complex situations. In the following chapters the principles developed there are extensively used in a comprehensive account of reactions of transition metal complexes, including reactions of biological signifacance. The text is illustrated by numerous figures and tables. Points of further interest are highlighted in special insets. 140 problems, taken from the original literature, enable the student to apply and deepen his newly acquired knowledge and make the book highly useful for courses in inorganic and organometallic reaction mechanisms. Furthermore, a wealth of over 1700 references renders it an indispensable work for the active researcher.
Author: Jay Dell Feldman
Publisher:
ISBN:
Category :
Languages : en
Pages : 454
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Author: Wilkins
Publisher:
ISBN:
Category :
Languages : en
Pages : 476
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Provides a comprehensive introduction to the field of chemistry, covering kinetic and mechanistic aspects of the reactions of transition metal complexes. Intended for academics, chemical institutes, inorganic chemists, and libraries, the text takes a problem/solution approach.
Author: Steven Krieger Grumbine
Publisher:
ISBN:
Category :
Languages : en
Pages : 384
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Author: Priyabrata Ghana
Publisher: Springer
ISBN: 9783030026240
Category : Science
Languages : en
Pages : 345
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This book explores the development of the first open-shell heavier tetrylidyne complexes featuring a tetrel-centered unpaired electron, and unprecedented metallatetrylidynes containing a multiply-bonded, linear-coordinated single heavier tetrel atom embedded between two metal centers. The chemistry of compounds featuring triple bonds of the heavier Group-14 elements Si–Pb with transition metals is a very challenging research area, which combines modern molecular main-group element with transition-metal chemistry, and is of fundamental importance for the understanding of chemical bonding. During the last 15 years, the research in this area has witnessed considerable progress in isolating a series of closed-shell tetrylidyne complexes. However, despite numerous attempts, open-shell tetrylidyne complexes and heavier group 14 element congeners of metallacarbynes and carbide complexes remained inaccessible. In this book, readers will find more about the reactivity studies of these novel complexes that uncovered a plethora of exceptional products, including a novel m3-silicido complex, the first dimetallasilacumulene with a linear, two-coordinated single silicon atom and the first compounds of planar tetracoordinated silicon (ptSi) (Anti-van’t Hoff-Le Bell Silicon). Readers will also learn about the isolation and full characterization of the first room-temperature stable disilavinylidene, a silicon analogue of the very reactive vinylidenes (R2C=C:), and the first intermetallic plumbylidyne ligand transfer reactions.
Author: Steven Raymond Klei
Publisher:
ISBN:
Category :
Languages : en
Pages : 442
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