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}].

International audience; 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 s…