Heats of formation of diphosphene, phosphinophosphinidene, diphosphine, and their methyl derivatives, and the mechanism of the borane-assisted hydrogen release

The high-level ab initio electronic structure theory is used to calculate the heats of formation of diphosphene (cis- and trans-[P.sub.2][H.sub.3]), phopshinophosphinidene (singlet and triplet [H.sub.2]PP) and diphosphine ([P.sub.2][H.sub.4]), and those of the [P.sub.2]H and [P.sub.2][H.sub.3] radicals ensuing from PH bond cleavages. The calculated results for the hydrogenation reactions have shown that substitution of an organic substituent for H improves the energetics, suggesting that secondary diphosphines and diphosphenes are potential candidates for use in a chemical hydrogen storage system.