Abstract: | Coordination polymerization of olefins has become an industrially important, yet still poorly understood enterprise. The ethylene polymerization activity of (neophyl)nZrCl4-n shows a twentyfold increase from n = 4 to n = 3 and a further tenfold increase to n = 2. The heterogeneous MR4/TiCl4 catalysts (M = Ti, R = benzyl; M = Zr, R = benzyl, neophyl) have been developed. To explore the breadth of extendability, other metal chlorides (main group and transition metal) were substituted for TiCl4. Indeed, excess AlCl3 or MgCl2 and the MR4 compounds also produced ethylene polymerization catalysts. The inactivity of corresponding (neophyl)4Ti systems is attributed to sterics. The abovementioned catalysts highlight the necessity of alkyl and chloride ligands at the transition metal catalyst centers. |