Quantum-chemical semiempirical calculations of 1-methylsilatrane

To ascertain the nature of the transannular Si N bond in molecules of the atrane type and the possibility of its description in semiempirical MO methods we calculated the 1-methylsilatrane (I), trimethylamine (II), triethylamine (III), triethanolamine (IV), trimethoxymethylsilane (V), triethoxymethylsilane (VI), and N,N-dimethylaminotrimethoxysilane (VII) molecules by the CNDO/2 and INDO methods (in sp and spd bases) and the MNDO method (in the sp basis). On the basis of an analysis of the electron density distribution and the compositions of the MO it was concluded that the transannular bond is due to the formation of a three-center N-Si-C/sub ax/ bond and an interaction with donor-acceptor character with the participation of the 3d AO of silicon and is weaker than the ordinary Si-Nin VII