G2(MP2) molecular orbital study of the substituent effect in the H3BPH3−nFn (n=0–3) donor–acceptor complexes

The complexation energies of H3BPH3−nFn (n=0–3) and the proton affinities of PH3−nFn compounds have been investigated at the G2(MP2) level of theory. G2(MP2) results show that the successive fluorine substitution on the phosphine increases the stability of H3BPH3−nFn complexes although the basicity of the PH3−nFn ligands reduces with this substitution. The NBO partitioning scheme shows that this stability was related to the hyperconjugation effect. It proves also that the shortening of the P–H and P–F bond lengths, upon complexation, is due to an increasing `sʹ character in these bonds.