J.A. Barker, D. Henderson, et al.
Molecular Physics
We have performed ab initio calculations to determine the degree of σ-basicity and π-acidity of a series of phosphorus ligands in model compounds of the type Pd-PX3, trans-L-Pd-PX3 and (CO)3Pd-PX3 with PX3 = P(CH3)3, PH3, P(OCH3)3, or PF3 and L = CO or NH3. We found that all the phosphine ligands considered are good σ-donors, with PF3 being only a moderately weaker base than P(CH3)3. In this respect, we demonstrate the inadequacy of the proton affinity as a measure of the σ-basicity of a ligand in zerovalent metal complexes. Alkylphosphine ligands are also good π-acceptors, but different from the σ-basicity, the π-acidity increases markedly along the series P(CH3)3 < PH3 < P(OCH3)3 < PF3. We have analyzed the extent to which the phosphorus 3d orbitals are directly involved in the bonding, in particular in the π-back-donation from the metal to the ligand. The P d functions are essential for a correct description of the metal-phosphorus bond. However, their role is that of polarization functions which can combine with the PX3 antibonding orbitals to form hybridized π-acceptor orbitals and not that of orbitals directly involved in the charge transfer from the metal. The π-acidity of P(CH3)3 and PH3 is considerably reduced upon removal of the phosphorus d functions. © 1992, American Chemical Society. All rights reserved.
J.A. Barker, D. Henderson, et al.
Molecular Physics
L.K. Wang, A. Acovic, et al.
MRS Spring Meeting 1993
Arvind Kumar, Jeffrey J. Welser, et al.
MRS Spring 2000
R.D. Murphy, R.O. Watts
Journal of Low Temperature Physics