Mechanistic studies on monodentate-ligand substitution of five-coordinate trigonal-bipyramidal platinum (II) complexes with tris[2-(diphenylphosphino)ethyl]phosphine

By investigating the equilibrium between trigonal-bipyramidal and square-pyramidal geometries of [Pt(pt)(pp3)](BF4) (pt = 1-propanethiolate, pp3 = tris[2-(diphenylphosphino)ethyl]phosphine) and the phosphine-bridging and chloro-ligand substitution reactions of [PtCl(pp3)]Cl, the reaction mechanism via a square-pyramidal intermediate with a dissociated terminal phosphino group and an apically coordinated entering halide ion has been disclosed for the trigonal-bipyramidal [PtX(pp3)]-type complexes.