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Synthesis and Reactions of Diphosphinidenecyclobutene Ruthenium Complexes Relevant to Catalytic Hydrosilylation of Terminal Alkynes

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Version 2 2016-06-03, 23:49
Version 1 2016-02-27, 13:02
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posted on 2008-05-26, 00:00 authored by Akito Hayashi, Takahiko Yoshitomi, Kazutoshi Umeda, Masaaki Okazaki, Fumiyuki Ozawa
The complex [RuCl(μ-Cl)(CO)(DPCB-OMe)]2 (1a), bearing a low-coordinated phosphorus ligand (DPCB-OMe = 1,2-bis(4-methoxyphenyl)-3,4-bis[(2,4,6-tri-tert-butylphenyl)phosphinidene]cyclobutene), is readily reduced to [RuH(μ-Cl)(CO)(DPCB-OMe)]2 (2a) by the reaction with water and HSiMe2Ph. The reaction proceeds via a [RuCl2(CO)(H2O)(DPCB-OMe)] intermediate, which is characterized by X-ray diffraction analysis. Complexes 1a and 2a serve as highly efficient catalysts for Z-selective hydrosilylation of phenylacetylene. The reason for the high catalyst efficiency of DPCB-OMe complexes has been investigated by reaction and structure analysis of the presumed intermediate [Ru(CHCHPh)Cl(CO)(DPCB-OMe)] (3a). It has been found that 3a has ample space to associate with hydrosilane and, therefore, readily undergoes metathesis between Ru−C and H−Si bonds. This structural feature in conjunction with the strong π-accepting ability of the DPCB-OMe ligand leads to highly efficient catalysis for Z-selective hydrosilylation of terminal alkynes.

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