ABINITIO INVESTIGATION OF THE STRUCTURES AND STABILITIES OF THE DONOR-ACCEPTOR COMPLEXES H3PBF3 AND ME3PBF3

The structures of the complexes H3PBF3 and Me3PBF3 are determined from ab initio electronic-structure calculations. In contrast to gas-phase experiments, H3PBF3 is found to give only a weak van der Waals complex with a P-B distance of 349 pm (SCF) and 322 pm (MP2), whereas the experimental value is 192 pm. The corresponding dissociation energies are 8.0 and 12.7 kJ/mol, respectively. These results are confirmed by coupled-pair functional calculations. The methods employed are checked by calculations on Me3PBF3, where deviations from experiment are in the expected range.