An ab initio nuclear magnetic resonance and atoms-in-molecules study of the PO bond in phosphine oxides

Ab initio nuclear magnetic resonance (NMR) calculations on the effect of correlation on phosphorus shielding in the phosphine oxides clearly suggest the absence of conventional multiple bonding in the PO bond. Atoms-in-molecules (AIM) studies that yield AIM-based localized molecular orbitals indicate one highly polarized sigma bond plus strong back-bonding of the oxygen pi orbitals, a picture consistent with a number of prior investigations. While it has been argued that the strong character of the PO bond in the phosphine oxides is highlighted best by the R3P=O formula, the present study indicates that the situation is better pictured as R3P+-O-.