Ab initio study on the thermochemistry of diphosphine (P2H4) and diphosphine radical cation (P2H+4)

The G2 calculated heat of formation of diphosphine, Δ Hf298 (H2PPH2) is 35.3 ± 8.3 kJ mol−1. This is closer to the earlier experimental estimates of 20.9 ± 4.2 kJ mol−1 and 41.4 kJ mol−1 than to the ΔHf298 value of 69 kJ mol−1 given in the widely used compilation of Lias et al. The diphosphine radical cation, H2PPH+2; has a non-planar C2h ground state structure and its heat of formation of H2PPH+2 (Δ Hf28) is 893.2 ± 2.0 kJ mol−1. The adiabatic ionization energy of diphosphine, H2P-PH2, was calculated using G2 theory to be 8.87 eV.