Reinvestigation of the Pd-catalysed bis(silylation) of alkynes with 1,1,2,2-tetramethyl-1,2-bis(phenylthiomethyl)disilane: Unexpected formation of the eight-membered siloxane-chelate complex cis-[PdCl2{(PhSCH2SiMe2)2O}]. - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Journal of Organometallic Chemistry Année : 2013

Reinvestigation of the Pd-catalysed bis(silylation) of alkynes with 1,1,2,2-tetramethyl-1,2-bis(phenylthiomethyl)disilane: Unexpected formation of the eight-membered siloxane-chelate complex cis-[PdCl2{(PhSCH2SiMe2)2O}].

Résumé

The bis(silylated) alkenes Z-(PhSCH2)Me2SiC(H)=C(Fc)SiMe2(CH2SPh) (2) and Z-(PhSCH2)Me2SiC(H)=C(bipheny)SiMe2(CH2SPh) (3) have been prepared by Pd-catalysed double silylation of ethynylferrocene and 4-ethynyl-1,1'-biphenyl in the presence of 1,1,2,2-tetramethyl-1,2-bis(phenylthiomethyl)disilane (1). A reinvestigation on the interaction of 1 with [PdCl2(PhCN)2] in technical-grade CH2Cl2 as solvent revealed competition between reduction to elemental palladium (due to oxidative addition of the Si-Si bond across Pd(II) and subsequent reductive elimination) and formation of an unusual eight-membered chelate complex cis-[PdCl2{(PhSCH2SiMe2)2O}] (4), which is fluxional in solution. Based on GC-MS analyses revealing both formation of chlorosilane ClSiMe2CH2SPh and the disiloxane (PhSCH2SiMe2)2O, residual water contained in CH2Cl2 is supposed to be the source of oxygen atom of the siloxane function. The mechanism of the formation of 4 is discussed. The molecular structures of 1 and 4 were determined by single-crystal X-ray diffraction analyses. The energies of several conformational isomers of 4 were computed by means of DFT calculations, the coexistence of a species featuring a weak dative Pd-O interaction due to a hemi-labile coordination of ligand 1 was evidenced.

Dates et versions

hal-00752165 , version 1 (15-11-2012)

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Harmel W. Peindy N'Dongo, Sébastien Clément, Sébastien Richeter, Fabrice Guyon, Michael Knorr, et al.. Reinvestigation of the Pd-catalysed bis(silylation) of alkynes with 1,1,2,2-tetramethyl-1,2-bis(phenylthiomethyl)disilane: Unexpected formation of the eight-membered siloxane-chelate complex cis-[PdCl2{(PhSCH2SiMe2)2O}].. Journal of Organometallic Chemistry, 2013, 724, pp.262-270. ⟨10.1016/j.jorganchem.2012.11.022⟩. ⟨hal-00752165⟩
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