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Abstract

A metallocene compound having the general formula: CpAXMQ.sub.1 Q.sub.2 Cp'A'X'M'Q.sub.1 'Q.sub.2 ' wherein Cp and Cp' are each independently a substituted or unsubstituted cyclopentadienyl moiety; M and M' are each independently a metal chosen from Group IV B transition metals and vanadium, and coordinate to Cp and Cp' respectively; X and X' are each independently a substituted or unsubstituted Group VA or VIA heteroatom and coordinate to M and M' respectively; A and A' are bridging groups between Cp and X and between Cp' and X' respectively and are independently chosen from --SiR'.sub.2 --O--SiR'.sub.2 --, --Si.sub.n R'.sub.m --, --C.sub.n R'.sub.m -- and --CR'.sub.2 --SiR'.sub.2 --CR'.sub.2 --SiR'.sub.2 --, in which each R' is independently H or hydrocarbyl having 1 to 20 carbon atoms, n is an integer in the range 1 to 4 and m=2n; each Q.sub.1, Q.sub.2 and Q.sub.1 ' and Q.sub.2 ' is independently a coordinating group which is hydrogen, halogen or hydrocarbyl having 1 to 20 carbon atoms and each of Q.sub.1 and Q.sub.1 ' is coordinated to both M and M'.

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First Claim