[sigma]- and [pi]-bond strengths in main group 3-5 compounds

Ab initio molecular electronic structure theory is used to calculate the [sigma]- and [pi]-bond strengths for the molecules B[H.sub.2]N[H.sub.2], B[H.sub.2]P[H.sub.2], Al[H.sub.2]N[H.sub.2] and Al[H.sub.2]P[H.sub.2]. The adiabatic [sigma]-bond energy is described as the dissociation energy of A[H.sub.2]X[H.sub.2] to A[H.sub.2] X[H.sub.2] in their ground states minus the adiabatic [pi]-bond energy.