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 's' character in these bonds.