Structure and chemical properties of mononuclear and dinuclear silylrhodium complexes. Activation of the Si–C bond and formation of Si–Cl and Si–SR bonds promoted by Rh complexes

Abstract

Recent studies of the structures and chemical properties of organosilylrhodium complexes are surveyed. Oxidative addition of secondary and tertiary silanes to chlororhodium(I) complexes with PMe 3 and with P( i-Pr) 3 ligands leads to the formation of chloro(hydrido)silylrhodium(III) complexes. The resulting Rh(III) complexes are often in equilibrium with Rh(I) complexes via a reversible reductive elimination of the organosilane and its reoxidative addition in solution. Irreversible coupling of chloro and silyl ligands of the complexes with an octahedral or a square-pyramidal Rh(III) center occurs at room temperature when the two ligands are at cis coordination sites. Complexes with chloro and organosilyl ligands at trans positions are thermally stable and release chlorosilanes upon heating above 80°C. Hydridorhodium(I) complexes formed in the above reaction mixture readily undergo oxidative addition of organosilane to give dihydrido(silyl)rhodium(III) complexes. Dinuclear silylrhodium(III) complexes, L(H)(Ar 3Si)Rh(μ-H)(μ-Cl)Rh(SiAr 3)(H)L (Ar=Ph, C 6H 4F; L=P( i-Pr) 3), prepared from the reaction of triarylsilane with RhCIl 2, cause thermally induced Si–C bond cleavage of a triarylsilyl ligand to afford L(H)Rh(μ-Cl)(μ-SiAr 3)(μ-SiAr 2)Rh(H)L, accompanied by the evolution of arene. The produced complexes contain a bridging triarylsilyl ligand coordinated symmetrically to the two Rh centers. RhH(SAr)(SiHAr′ 2)(PMe) 3-type complexes with thiolato and diarylsilyl ligands at trans positions undergo clean thermal rearrangement to give complexes with the Si(SAr)Ar′ 2 ligand. The Rh complex that promoted the Si–S bond forming reaction is extended to the synthesis of a new disilarhodacyclopentane and to the RhCl(PPh 3) 3-catalyzed polycondensation of diarylsilane with dithiols to form new Si-containing polymers.