Preparation and properties of sandwiched trinuclear palladium(II) complexes with tridentate phosphine and phosphine sulfide ligands

摘要

The central phosphino group of tripodal tetradentate tris[2- (diphenylphosphino)ethyl]phosphine (pp3) was selectively oxidized by the reaction with diethyl disulfide to give tridentate phosphine ligand pOp _3. The terminal phosphino groups were reacted with sulfur to give pOp_3 trisulfide (pOp_3S_3). Three palladium(II) ions were sandwiched in the two pOp_3 and pOp3_S_3 ligands to form the trinuclear complexes with three trans(P) and trans(S) PdX_2 (X = Cl, Br, I) moieties, respectively. The tripodal triphosphine, 1,1,1-tris(diphenylphosphinomethyl)ethane (i-p_3), and its mono- and tri-sulfide, which have shorter carbon chains compared with pOp_3, form the mononuclear dichloro palladium(II) complexes with cis(P) and cis(S) geometries. Difference in the catalytic activity for the C-C coupling reaction was discussed in connection with the coordinated groups and geometries of the complexes.