MOLECULAR GEOMETRIES AND ENERGETICS OF MONOLIGATED AND BILIGATED GROUP-2 METAL MONOPOSITIVE IONS USING AN IMPROVED ASED-MO MODEL

The structural, energetic and spectroscopic properties of the complete series of ML(n)(+) (n = 1 or 2; L = H2O, NH3, CH3OH and CO) and MLL'(+) (L' = H2O, NH3 and CH3OH) complexes of group 2 metal monopositive ions have been calculated by an improved ASED-MO model. Accurate metal-ligand stretching and ligand-metal-ligand bending potential energy curves were derived for all cationic species. The computed spectroscopic properties (R(e), D-e, omega(e) and theta) by the new semiempirical computational scheme were found to be in good agreement with those of ''state-of-the-art'' ab initio calculations, where available. Calculations were consistent with a predominantly ionic character of the bonding in both the mono- and biligated group 2 metal cations. Moreover, they provided evidence for synergic stabilization of the mixed-ligand biligated systems and the existence of trans effect in coordination compounds of main group metal ions.