Organosilicon chemistry. Part XII. Stability and catalytic activity of some chlorohydridobis(phosphine)(silyl)rhodium(III) complexes

Abstract

New complexes of the type [L₂RhH(SiR₃)Cl] have been prepared [L = Ph₂(tol)P, Ph₂(cy)P, Ph(cy)₂P, or Ph₂PrⁱP; R = OEt, Me, or Et; tol =p-tolyl; cy = cyclohexyl]. Evidence for similar complexes with L = Ph₂EtP and Ph₂MeP has been obtained by ligand-exchange studies. The stability to dissociation of complexes of this type increases in the orders SiMe₃ < SiMe₂Cl < SiMeCl₂ < SiCl₃, SiPh₃ < SiEt₃ < Si(OEt)₃ < SiCl₃, (cy)₃P < Ph(cy)₂P < Ph₂(cy)P ≲ Ph₂(tol)P ≈ Ph₃P, Ph₂MeP < Ph₂EtP < Ph₂PrⁱP ≈ Ph₃P, and Ph₃As < Ph₃P. The dependence of stability on the neutral ligand reflects a combination of steric and electronic effects. The rate of addition of triethylsilane to hex-1-ene, catalysed by the complexes [L₃RhCl], increases in the order L =(cy)₃P Ph₂MeP < Ph(cy)₂P ≈ Ph₃P < Ph₂(cy)P ≈ Ph₂EtP.