Analysis of changes in 3 5 Cl NQR frequency of complexes MCl 4 .L and MCl 4 .2L for M = Si, Ge, Sn and Ti was performed. The population of the atomic orbitals was calculated by the quantum chemistry methods PM3 and INDO. The results provided an explanation of the changes in 3 5 Cl NQR frequency and the asymmetry parameter upon complex formation. In the complexes of non-transition elements, a decrease in 3 5 Cl NQR frequency is first of all related to increasing population of p z orbitals on Cl atoms. In the complexes of Ti, the increase in 3 5 Cl NQR frequency depends on a decrease in the p π to d π electron density transfer.