Organosilicon chemistry. Part V. Rhodium(III)–silyl complexes and the hydrosilation of hex-1-ene

Abstract

Complexes of the type (Ph₃M)₂RhH(SiR₃)X [M = P, R = Cl, OEt(X = Cl, Br, l), R₃= Cl₂Me, Cl₂Et, ClMe₂, ClEt₂,Et₃(X = Cl, Br), R₃= Me₃, Ph₃(X = Cl). M = As, Sb, R = Cl, OEt(X = Cl)] are obtained by direct reaction between the appropriate silane and (Ph₃M)₃RhX. The stability of the phosphine complexes to thermal decomposition and to dissociation in solution varies widely from R = Cl or OEt (very stable) to R = alkyl or phenyl (completely dissociated in solution). The presence of a Rh—H bond is demonstrated by infrared and ¹H n.m.r. spectroscopy (ν_Rh–H 2020–2130 cm.^–1, J_Rh–H 21–27 c./sec., J_P–Rh–H 13–15 c./sec.), and a monomeric, five-co-ordinate structure is proposed. The complex (Ph₃P)₂RhH(SiCl₃)Cl reacts with CO or PF₃ to give SiHCl₃ and (Ph₃P)₂Rh(L)Cl (L = CO, PF₃), and evidence for the formation of the very unstable complex (Ph₃P)₂Rh(CO)Cl(H)SiCl₃ is presented. The complex (Ph₃P)₂RhH[Si(OEt)₃]Cl reacts with anhydrous hydrogen chloride to give SiH(OEt)₃ and (Ph₃P)₂RhHCl₂. The catalysis of the addition of R₃SiH (R = Ph, Et, Cl) to hex-1-ene by (Ph₃P)₃RhCl and by (Ph₃P)₂RhH(SiCl₂Et)Cl is discussed.