Theoretical calculations of nuclear spin coupling of phosphorus to carbon and hydrogen by the finite perturbation method

Abstract

AbstractFinite perturbation calculations using CNDO/2 wave functions are presented for the determination of 31P13C and 31P1H couplings. The calculations were carried out on 46 molecules and a comparison with experimental values is given. The groups of compounds considered were phosphonium cations, phosphine oxides, alkylidenephosphoranes, phosphine sulfides, phosphoranes and phosphines. With the exception of phosphines, the finite perturbation approach reproduces the experimental couplings with fair accuracy. It is found that there is a good correlation with the calculated 1J(P, C) and the phosphorus 3s‐carbon 2s bond orders for tetra‐ and pentavalent phosphorus compounds. This lends support to the growing body of evidence for the direct relationship of the magnitude of 1J(P, C) and percent s character in the hybrid orbital on the carbon comprising the PC bond. The finite perturbation technique was also used to explore the effects of geometrical changes on PC and PH couplings. Finally, the effect of deleting d orbitals on phosphorus is discussed briefly.