Geminal Interactions in ClZ(CH_3)_2X Molecules (Z =C,Si,Ge)According to ab initio Calculations

摘要

The structure and electronic parameters of ClZ(CH_3)_2X molecules (Z=C,Si,Ge;X=CH_3,OCH_3)were calculated by the RHF/6-31G(d)and RHF/6-311G(d,p)methods with full geometry optimization;calculations of ClZ(CH_3)_2OCH_3 molecules were also performed by the RHF/6-31G(d)method with partial geometry optimization.The~(35)Cl NQR frequencies calculated from the populations of less diffuse 3p constituents of valence p orbitals of chlorine [RHF/6-31G(d)]were in agreement with the experimental values.The ~(35)Cl NQR frequencies for molecules with X=OCH_3 are lower than those for molecules with X=CH_3 (the Z atom being the same),due mainly to direct through-field polarization of the Z-Cl bond,induced by the effect of unshared electron pair of the oxygen atom in the trans position with respect to that bond.The difference in the ~(35)Cl NQR frequencies decreases in going from Z=C to Z =Si,Ge,in parallel with variation of the Z-Cl bond polarization as the size of Z increases.