NATURE OF THE SEMIPOLAR XO BOND - COMPARATIVE ABINITIO STUDY OF H3NO, H2NOH, H3PO, H2POH, H2P(O)F, H2SO, HSOH, HCLO, ARO, AND RELATED MOLECULES

Ab initio calculations with various basis sets (of double-ζ quality augmented by polarization functions) were performed on SCF level, and with the inclusion of electron correlation, for the molecules H3NO, H3PO, H2SO, HCIO, and ArO, some isomers such as H2NOH, H2POH, and HSOH, some fluorine-substituted compounds such as H2P(O)F, and the corresponding oxygen-free molecules. The results are analyzed in terms of binding energies for the XO bonds, contributions of dAOs to the bonds, effective charges, and overlap populations (according to Mulliken and Heinzmann-Ahlrichs). The most relevant geometrical parameters are optimized and computed dipole moments are given. Conclusions are drawn concerning the nature of the XO bond in the various compounds. Although there are large differences, e.g., between H3NO and H3PO, all these bonds are essentially semipolar of the type X+-0-. dAOs have a significant contribution in H3PO, H2P(O)F, and H2SO, but it is not justified to regard them as valence AOs. The isomers H2NOH, H2POH, and HSOH are lower in energy than H3NO, H3PO, and H2SO, respectively, although the energy difference of the pair H2POH/H3PO is very small. The XO bond is stabilized both by CH3 and F substitution, though the stabilization mechanisms are quite different. A comparison to bonding in phosphoranes and related compounds is also made. For H3N, H3P, H3NO, and H3PO the correlation energy is analyzed. Copyright © 1979, American Chemical Society. All rights reserved.