Computational Studies of Open-Shell Phosphorus Oxyacids 1. P-H Bond Homolysis in H₂PO₂

Cramer, C. J.; Famini, G. R.
J. Am. Chem. Soc. 1990, 112, 5460.

The hypothetical molecule dihydrodioxophosphoranyl, 1, has been studied computationally. Both 3-21G⁽*⁾ and 6-31G* unrestricted Hartree-Fock (UHF) wavefunctions exhibited inherent doublet instability which was corrected for by consideration of correlation effects. Configuration interaction proved most effective in this respect, while Moller-Plesset perturbational corrections were fair when extended to third order and only marginal when truncated at second order. The barrier to P-H bond homolysis was determined to be 4.8 +/- 0.3 kcal/mole. The metastability of 1 has been explained in the formalism of valence bond theory. It arises from interactions of degenerate valence bond functions corresponding to reactants and products with an intermediate configuration corresponding to a n -> pi* (1A2 -> 3B1) excited state. Predicted spectral data to aid in the identification of 1 are presented.