CHEMICAL BONDING IN HYPERVALENT MOLECULES REVISED - APPLICATION OF THE ATOMS IN MOLECULES THEORY TO Y-3 X AND Y-3 XZ (Y = H OR CH3 X = N, POR AS Z = O OR S) COMPOUNDS

Atoms in Molecules Theory has been applied to analyze bonding properti es, in potentially hypervalent pnicogen (N, P or As)-chalcogen(O or S) bonds within the framework of three plausible models: (i) one sigma b ond and two pi back-bonds (negative hyperconjugation), (ii) one sigma bond and three pi back-bonds, and (iii) three Omega (banana) bonds. Th e topological analyses (based upon the electron charge density (rho(r) ), its Laplacian (del(2)rho(r)), bond ellipticity, etc.) ana the charg es were consistent with a highly polarized sigma bond, with;bond stren gth dependent on the electrostatic interactions. The equilibrium geome tries were optimized by both density functional theory with a hybrid f unctional (B3LYP) and by ab initio methods at the MP2(full) level, usi ng the 6-311G basis set augmented by polarization and/or diffuse funct ions.