- Synthesis and Hydrogenation of Heavy Homologues of Rhodium Carbynes: [(Me3P)2(Ph3P)Rh≡E-Ar*] (E=Sn, Pb)
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Tetrylidynes [(Me3P)2(Ph3P)Rh≡SnAr*] (10) and [(Me3P)2(Ph3P)Rh≡PbAr*] (11) are accessed for the first time via dehydrogenation of dihydrides [(Ph3P)2RhH2SnAr*] (3) and [(Ph3P)2RhH2PbAr*] (7) (Ar=2,6-Trip2C6H3, Trip=2,4,6-triisopropylphenyl), respectively. Tin dihydride 3 was either synthesized in reaction of the dihydridostannate [Ar*SnH2]? with [(Ph3P)3RhCl] or via reaction between hydrides [(Ph3P)3RhH] and (Formula presented.) [(Ar*SnH)2]. Homologous lead hydride [(Ph3P)2RhH2PbAr*] (7) was synthesized analogously from [(Ph3P)3RhH] and (Formula presented.) [(Ar*PbH)2]. Abstraction of hydrogen from 3 and 7 supported by styrene and trimethylphosphine addition yields tetrylidynes 10 and 11. Stannylidyne 10 was also characterized by 119Sn M?ssbauer spectroscopy. Hydrogenation of the triple bonds at room temperature with excess H2 gives the cis-dihydride [(Me3P)2(Ph3P)RhH2PbAr*] (12) and the tetrahydride [(Me3P)2(Ph3P)RhH2SnH2Ar*] (14). Complex 14 eliminates spontaneously one equivalent of hydrogen at room temperature to give the dihydride [(Me3P)2(Ph3P)RhH2SnAr*] (13). Hydrogen addition and elimination at stannylene tin between complexes 13 and 14 is a reversible reaction at room temperature.
- Widemann, Max,Eichele, Klaus,Schubert, Hartmut,Sindlinger, Christian P.,Klenner, Steffen,P?ttgen, Rainer,Wesemann, Lars
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supporting information
p. 5882 - 5889
(2021/02/03)
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- Construction of a visible light-driven hydrocarboxylation cycle of alkenes by the combined use of Rh(i) and photoredox catalysts
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A visible light driven catalytic cycle for hydrocarboxylation of alkenes with CO2 was established using a combination of a Rh(i) complex as a carboxylation catalyst and [Ru(bpy)3]2+ (bpy = 2,2′- bipyridyl) as a photoredox catalyst. Two key steps, the generation of Rh(i) hydride species and nucleophilic addition of π-benzyl Rh(i) species to CO2, were found to be mediated by light.
- Murata, Kei,Numasawa, Nobutsugu,Shimomaki, Katsuya,Takaya, Jun,Iwasawa, Nobuharu
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p. 3098 - 3101
(2017/03/17)
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- Using NMR and ESI-MS to probe the mechanism of silane dehydrocoupling catalyzed by wilkinson's catalyst
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The reaction of Wilkinson's catalyst Rh(PPh3)3Cl (1) with 1-2 equiv. of di-n-hexylsilane gives rise to a complex mixture of products, which has been analyzed by 31P{1H} NMR and shown to include the hydrido complex Rh(PPh3)3H (3). Continuous sampling of the 1:1 reaction mixture by ESI-MS provided time-dependent speciation that tracks the formation of 3 at the expense of the initial silane oxidative addition product [Rh(PPh3)2(Cl)(H){Si(nHex) 2H}] (2), the subsequent 1st order disappearance of 3, and the formation of other, minor side-products. Our results provide insight into established activity of 1 for catalytic dehydrocoupling of di-n-hexylsilane, and implicate complex 3 as the active species in this catalysis. The combination of 31P NMR and ESI-MS provides detailed insight into the dynamics of the activation of a secondary silaneby Rh(PPh3)3Cl, with strong evidence pointing to the role of Rh(PPh3)3H as the active catalyst for silane dehydrocoupling and to the deleterious effect of trace water in this system. Copyright
- Jackson, Sarah M.,Chisholm, Danielle M.,McIndoe, J. Scott,Rosenberg, Lisa
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p. 327 - 330
(2011/05/07)
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- Synergistic effects of two Si-H groups and a metal center in transition metal-catalyzed hydrosilylation of unsaturated molecules: A mechanistic study of the RhCl(PPh3)3-catalyzed hydrosilylation of ketones with 1,2-bis(dimethylsilyl)benzene
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Three rhodadisilacyclopentene complexes are synthesized by the reaction of 1,2-bis(dimethylsilyl)-benzene with RhCl(PPh3)3 or Rh(H)(PPh3)4, and their contributions to the catalytic hydrosilylation of acetone are discussed. Treatment of the rhodium precursor RhCl(PPh3)3 or Rh(H)(PPh3)4 with 1,2-bis(dimethylsilyl)benzene affords an unstable Rh(V)-trihydride species having a rhodadisilacy-clopentene skeleton, Rh(Me2SiC 6H4SiMe2)(H)3(PPh3) 2 (1), as a primary product, which is formed by double oxidative addition of 1,2-bis(dimethylsilyl)benzene to the rhodium center. The complex 1 eliminates H2 upon concentration to quantitatively form a Rh(III)-monohydride complex, Rh(SiMe2C6H 4SiMe2)(H)(PPh3)2 (2). Further oxidative addition of 1,2-bis(dimethylsilyl)benzene to 2 gives a Rh(III)-trisilyl complex, Rh(Me2SiC6H4SiMe 2)(η1-HSiMe2C6H 4SiMe2)(PPh3) (3), in which there is an agostic interaction between the Si-H bond and the Rh(III) center. Elimination of H 2 from 1 is reversible, and the most effective method for preparing 1 in solution is found to be treatment of 2 with H2. The catalytic behavior of these three new rhodadisilacyclic complexes, RhCl(PPh 3)3, and Rh(H)(PPh3)4, in the hydrosilylation of acetone with 1,2-bis(dimethylsilyl)benzene was studied. The results suggest the important contribution of the trihydride 1 in the synergistic effect of two proximate Si-H bonds, leading to an unusual rate enhancement in the hydrosilylation of acetone with 1,2-bis(dimethylsilyl) benzene.
- Sunada, Yusuke,Fujimura, Yoshiki,Nagashima, Hideo
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p. 3502 - 3513
(2009/02/05)
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