Experimental and calculated vibrational spectra and structure of Ziegler-Natta catalyst precursor: 50/1 comilled MgCl2-TiCl4

The vibrational Infrared and Raman Spectra of a MgCl₂-TiCl₄ Ziegler-Natta catalyst precursor with a 50/1 MgCl₂/TiCl₄ ratio have been recorded. The Raman spectrum of this catalyst precursor, in the range 50-500 cm⁻¹, shows clear scattering lines which can be assigned to the complex MgCl₂-TiCl₄, well separated from those of the initial species. Analogous, but less clear signals can be found in the infrared spectrum. Vibrational symmetry analysis and quantum chemical calculations of suitable models of MgCl₂-TiCl₄ complex have been made for the interpretation of the experimentally recorded spectra. The observed spectroscopic signals can be explained in terms of the existence of only one type of MgCl₂-TiCl₄ complex where the TiCl₄ molecules are complexed on the MgCl₂ along the (110) lateral cuts in a local C_2v symmetry with the Ti atoms in an octahedral coordination.