A highly effective catalyst system for the polymerization of olefins comprises a cocatalyst, preferably an aluminoxane, and a metallocene of the formula I ##STR1## where M.sup.1 =Zr or Hf, R.sup.1 and R.sup.2 =(C.sub.1 -C.sub.3)-alkyl or chlorine, R.sup.3, with the proviso that at least one of the radicals R.sup.3 is not hydrogen, is hydrogen, F, Cl, --OR.sup.7, --NR.sup.7 R.sup.8, --P(O)R.sup.7 R.sup.8, --P(OR.sup.7).sub.2 or SR.sup.7, R.sup.4 is a ##STR2## radical, and m plus n are zero or 1.
一种高效的烯烃聚合催化剂体系,包括一个辅助催化剂,优选为铝氧烷,以及一个具有公式I的
金属茂化合物:其中M1=Zr或Hf,R1和R2=(C1-C3)-烷基或
氯,R3至少一个基团不是氢,而是氢、F、Cl、-OR7、-NR7R8、-P(O)R7R8、-P(OR7)2或SR7,R4是一个##STR2##基团,m和n为0或1。