THE ASYMMETRY PARAMETER OF THE ELECTRIC-FIELD GRADIENT TENSOR OF TICL4 AND ITS COMPLEXES STUDIED BY NQR NUTATION SPECTROSCOPY

Nuclear Quadrupole Resonance (NQR) Nutation Spectroscopy studies and I NDO calculations of the electronic structure of TiCl4 and its complexe s have been performed. An explanation of the changes of the NQR freque ncies and asymmetry parameters upon complex formation have been propos ed. The populations of the TiCl4 orbitals have been estimated for diff erent crystallographic structures and compared with the population of the TiCl4.2CH(3)CN orbitals. The values of the experimental Cl-35 NQR frequencies correlated with the calculated ones. Moreover, there is go od agreement between the experimentally determined and calculated nuta tion spectra asymmetry parameter for TiCl4. The results of the INDO ca lculations showed that the Ti-Cl bond order decreases upon complex for mation and consequently the Cl-35 NQR frequencies decrease and the asy mmetry parameter increases. On the basis of the results of the quantum chemical calculations the population of the 3p(pi) chlorine orbital d ecreases when the molecular structure changes from TiCl4 (T-d) to TiCl 4 (D-4h) The electron density transfer from the p(pi) orbital of the c hlorine atom to the d(pi) orbital of the Ti atom decreases due to comp lex formation. It was found that the INDO method is suitable for deter mining the electron distribution in TiCl4 and its complexes. (C) 1997 Elsevier Science B.V.