METALLOCENE ANALOGS CONTAINING BULKY HETEROALLYLIC LIGANDS AND THEIR USE AS NEW OLEFIN POLYMERIZATION CATALYSTS

A series of Ti and Zr metallocene analogues containing bulky benzamidi nate ligands has been prepared and fully characterized, Treatment of T iCl4(THF)(2) or ZrCl4(THF)(2) with two equivalents of the appropriate benzamidinate anions affords the bis(benzamidinato) complexes [C6H5C(N C3H7)(2)](2)MCl2 (M = Ti (1), Zr (2)) and [C6H5C(NC6H11)(2)](2)MCl2 (M = Ti (3), Zr (4)). Tne zirconium complex 2 was structurally character ized by X-ray diffraction. In a similar manner the nonafluoromesityl d erivative [(CF3)(3)C6H2C(NC6H11)(2)](2)ZrCl2 (5) was synthesized from ZrCl4(THF)(2) and Li[(CF3)(3)C6H2C(NC6H11)(2)]. Methylation of 4 with methyllithium yields the dimethyl complex [C6H5C(NC6H11)(2)](2)ZrMe2 ( 6). The mixed-ligand metallocene analogues [C6H5C(NC3H7)(2)](C5Me5)MCl 2 (M = Ti (7), Zr (8)) and [C6H5C(NC6H11)(2)](C5Me5)TiCl2 (9) have bee n prepared by reacting (C5Me5)TiCl3 or (C5Me5)ZrCl3 with one equivalen t of a lithium N, N ''-dialkylbenzamidinate. The polymerization of eth ylene and propylene has been studied by the catalytic precatalyst comp lexes 1 and 2 upon reaction of an excess of methylalumoxane to obtain the active cationic complexes. The polymerization activity of the comp lexes is comparable to other benzamidinate ancillary containing ligand s although toward shorter amounts of time due to a competitive inhibit ion presumably obtained by a P-hydrogen elimination from the ligand. P olymerization activity is strongly dependent on catalyst and cocatalys t concentrations and on temperature. (C) 1998 Elsevier Science B.V.