THEORETICAL INVESTIGATIONS ON HETEROGENEOUS ZIEGLER-NATTA CATALYST SUPPORTS - STABILITY OF THE ELECTRON-DONORS AT DIFFERENT COORDINATION SITES OF MGCL2

Ab initio methods were used to study the coordination of electron dono rs to the (110) and (101) surfaces of a MgCl2 support. The electron do nors were alcohols, ketones, esters, and their model compounds. Examin ation of the interaction energies indicated that the alcohols bind mor e strongly to the five-coordinated magnesium atom on the (101) surface than to the four-coordinated magnesium atom on the (110) surface. Thi s stability on the (101) surface can be explained in terms of hydrogen bonding between the complexed alcohol and a chloride ion of the surfa ce. Like the alcohols, the esters form the most stable complexes on th e (101) surface. In contrast, the ketones coordinate preferably to the (110) surface. The geometries of these coordinated electron donors ca n be predicted fairly reliably even with small model compounds. In the case of the alcohols, the coordination angle between the donor and th e surface depends on the number of alcohols on the same magnesium atom .