Theoretical investigation of (MgCl₂)_x polynuclear species formed during preparation of MgCl₂-supported Ziegler-Natta catalysts from solid solvates

A novel approach for the study of the nature of the active species in Ziegler-Natta catalysis is described. This approach is based on the study of reliable structural models for disordered (MgCl₂)_x polynuclear species which develop during the preparation of MgCl₂-supported catalysts starting from MgCl₂-Lewis-base adducts, and the calculation of X-ray diffraction patterns of these models. A method for the calculation of the X-ray powder diffraction patterns of the model structures is devised. This diffraction modelling method may be useful for the correct interpretation of the nature of some diffraction features in the X-ray diffraction patterns recorded during the structural evolution of MgCl₂-Lewis-base adducts, which occurs in the preparation of the catalyst systems used for Ziegler-Natta polymerization of olefins.