STEREOCHEMISTRY OF THE INITIATION STEP IN ZIEGLER-NATTA CATALYSTS CONTAINING DIALKYL PROPANE DIETHERS - A TOOL FOR DISTINGUISHING THE ROLE OF INTERNAL AND EXTERNAL DONORS

The results of a study on a new generation of MgCl2 supported Ziegler- Natta catalysts that contain dialkyl propane diethers as internal dono rs and produce highly stereospecific polypropene even without any exte rnal donor are presented. The results concerning three different catal ysts containing 2,2-diisobutyl-1,3-dimethoxy propane (DIBDMP), 2,2-dic yclopentyl-1,3-dimethoxy propane (DCPDMP) and 2-ethyl,2-butyl-1,3-dime thoxy propane (EBDMP) as internal donors are compared. The same donors have also been studied by using them as external donors with a cataly st contaning diisobutyl phthalate as internal donor. The present resul ts, along with previously obtained findings on traditional supported Z iegler-Natta catalysts, permit a general comprehension of the role of internal and external donors.