307313-17-3Relevant academic research and scientific papers
Rate and mechanism of the oxidative addition of a silylborane to Pt 0 complexes - Mechanism for the Pt-catalyzed silaboration of 1,3-cyclohexadiene
Durieux, Guillaume,Gerdin, Martin,Moberg, Christina,Jutand, Anny
, p. 4236 - 4241 (2008)
The chemical reduction of Pt(acac)2 by DIBALH in the presence of phosphanes, which is used to generate active Pt0 complexes in the Pt-catalyzed silaboration of cyclohexadiene by 2-(dimethylphenylsilyl)-4,4,5,5- tetramethyl-1,3,2-dioxaborolane (1) leading to the 1,4-silaborated product, was mimicked by the electrochemical reduction of Pt(acac)2 in the presence of 2 equiv. of PR3 (R = Ph, nBu). The electrochemical reduction generates free acac anions and neutral Pt0-(PR 3)2 complexes. The kinetics of the oxidative addition of bromobenzene (used first as a model molecule) and silylborane 1 to the Pt 0 complexes was investigated and the rate constants determined. Pt0(PnBu3)2 is much more reactive than Pt 0(PPh3)2 towards 1. From the electrochemical study, it emerges that the acac anions released in the reduction of Pt(acac)2 do not coordinate to the Pt0(PR 3)2 complexes. Consequently, the rate of the oxidative addition of 1 to Pt0(PR3)2, generated either by the electrochemical reduction or by the chemical reduction by DIBALH, is not affected by the acac anions and a posteriori not by aluminum cations. The oxidative addition and the further step of the catalytic cycle [insertion of the diene into the Pt-B bond of the Si-Pt-B complex generated in the oxidative addition, with formation of the (η3-allyl)Pt-Si complex] were monitored by NMR spectroscopy. Pt0 and PtII complexes involved in the catalytic cycle were characterized. The oxidative addition is faster when the ligand is PMe2Ph relative to that obtained with PPh3, in agreement with the electrochemical data. No reductive elimination within the (η3-allyl)Pt-Si complex is observed when the ligand is PMe2Ph, whereas reactions in the presence of PPh 3 proceeded to give the final product. As a consequence, PPh 3 is a better ligand than PMe2Ph for the catalytic reaction, as observed experimentally. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
Transition metal silyl complexes. Part 63. Influence of the phosphane ligands and the metal complex geometry on the silyl group exchange between L2Pt(SiMe2Ph)2 (L2 = R2PCH2CH2PR2 or 2PR3) and HSiR'3
Kalt, Dominique,Schubert, Ulrich
, p. 211 - 214 (2008/10/08)
The exchange of the silyl ligands upon reaction of [(κ2-P,P)-R2PCH2CH:PR2]Pt(SiMe2Ph)2 (R = Ph, Me, cyclohexyl) with HSi(OMe)3 or 1,2-bis(dimethylsilyl)benzene was investigated by NMR spectroscopy. The exchange rate is considerably lower than in the complexes cis-(R3P)2Pt(SiMe2Ph)2, and decreases in the order R = Ph > Me > cyclohexyl. No exchange was observed in the analogous reactions of trans-(R3P)2Pt(SiMe2Ph)2. The isomerization of cis-(PhMe2P)2Pt(SiMe2Ph)2 into trans-(PhMe2P)2Pt-(SiMe2Ph)2 is catalyzed by di- and oligosilanes. (C) 2000 Elsevier Science S.A.
