Pseudopotential Calculations. 5. Results for Group 2A and 2B Dimethyls and Chlorides

Ab initio valence-only molecular orbital calculations, using an ab initio pseudopotential to represent the cores, are reported for (CH3)2Mg, (CH3)2Zn, ZnCl2, MgCl2, CH3MgCl, and ZnF2, all at experimental (electron diffraction) geometries. The calculations were performed in an attempt to study the effects on the bonding of the full 3d and 3p orbitals which distinguish these compounds. We find that, as expected, the bonding is nearly all of σ type; the d electrons in Zn seem unimportant for these bicoordinate species. Orbital energies and population analysis are contrasted with expectations based on electronegativities and Pearson's hard-soft principle; the latter seems slightly more helpful. The somewhat unusual bond distances reported in the literature are briefly discussed.