Characterization of sigma and pi donation of solvents by P-31 NMR chemical shifts of trigonal-bipyramidal Palladium(II) complexes with tris(2-diphenylphosphinoethyl)phosphine

The formation of the trigonal-bipyramidal palladium(II) complexes with tris(2-diphenylphosphinoethyl)phosphine pp(3) and one solvent molecule, [Pd(pp(3))(solvent)](2+) (solvent=acetonitrile, pyridine, dimethyl sulfoxide, N,N-dimethyl-formamide, trimethylphosphite), is confirmed by the P-31 NMR spectroscopy. In these complexes, the central phosphorus atom in the pp(3) ligand and the solvent molecule are coordinated in the axial position, and the terminal phosphorus atoms in the pps ligand are in the equatorial plane. The P-31 NMR chemical shifts of the axial and equatorial phosphorus atoms are quite sensitive to the axially coordinated solvent. The sigma and pi donations of the solvents were characterized by using the P-31 NMR chemical shifts.