Metallocenes having benzo-fused indenyl derivatives as ligands, processes for their preparation and their use as catalysts

A compound of the formula I ##STR13## in which M.sup.1 is a metal of group IVb, Vb or VIb of the periodic table,

• R.sup.1 and R.sup.2 are identical or different and are a hydrogen atom, a C.sub.1 -C.sub.10 -alkyl group, a C.sub.1 -C.sub.10 -alkoxy group, a C.sub.6 -C.sub.10 -aryl group, a C.sub.6 -C.sub.10 -aryloxy group, a C.sub.2 -C.sub.10 -alkenyl group, a C.sub.7 -C.sub.40 - arylalkyl group, a C.sub.7 -C.sub.40 -alkylaryl group, a C.sub.6 -C.sub.40 -arylalkenyl group, an OH group or a halogen atom,
• the radicals R.sup.3 are identical or different and are a hydrogen atom, a halogen atom, a C.sub.1 -C.sub.10 -alkyl group, which can be halogenated, a C.sub.6 -C.sub.10 -aryl group or an --NR.sub.2, --SR, --OSiR.sub.3, --SiR.sub.3 or --PR.sub.2 radical, in which R is a halogen atom, a C.sub.1 -C.sub.10 -alkyl group or a C.sub.6 -C.sub.10 -aryl group,
• R.sup.4 to R.sup.10 have the meaning given for R.sup.3, or adjacent radicals R.sup.4 to R.sup.10 with the atoms joining them, form an aromatic or aliphatic ring, and ##STR14## in which R.sup.12 and R.sup.13 are identical or different and are a hydrogen atom, a halogen atom, a C.sub.1 -C.sub.10 -alkyl group, a C.sub.1 -C.sub.10 -fluoroalkyl group, a C.sub.6 -C.sub.10 -aryl group, a C.sub.6 -C.sub.10 -fluoroaryl group, a C.sub.1 -C.sub.10 -alkoxy group, a C.sub.2 -C.sub.10 -alkenyl group, a C.sub.7 -C.sub.40 -arylalkyl group, a C.sub.8 -C.sub.40 -arylalkenyl group or a C.sub.7 -C.sub.40 -alkylaryl group, or R.sup.12 and R.sup.13, in each case with the atoms joining them, form a ring, and
• M.sup.2 is silicon, germanium or tin.