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

Abstract

The central phosphino group of tripodal tetradentate tris[2-(diphenylphosphino)ethyl]phosphine (pp 3) 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 pOp 3S 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.