Metallocene catalysts comprising indenyl ligands substituted with electronegative groups

摘要

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.