Catalyst combination and a process for preparing linear, isotactic polymers

A catalyst combination for preparing linear isotactic polymers, said catalyst combination containing a metal complex of general Formula I

• 4
• wherein the substituents have the following significations:
• R1-R7 linear or branched C1 to C10 alkyl, 5- to 7-linked cycloalkyl which, in its turn, can carry one or several C1 to C6 alkyl residues as substituent, C6 to C18 aryl or arylalkyl or alkylaryl, in which case R1/R2, R3/R4, R6/R7 can be partially or simultaneously integrated into 5- to 7-linked cycloalkyl or aryl rings fused thereto;
• R9, R10 C1 to C8 alkyl, 4- to 7-linked cycloalkyl, aryl, in which case R9, R10 can, jointly with E, form a 4- to 7-linked cycloalkyl or aryl;
• R11 C1 to C8 alkyl, aryl, C1 to C8 oxyalkyl, C1 to C8 trialkylsiloxy;
• M titanium, zirconium, hafnium, vanadium, niobium, tantalum;
• X halogen or C1 to C8 alkyl, aryl, benzyl;
• E carbon, silicon, germanium or 1.2-ethyl 1.3-propyl, 1.4-butyl;
• and an activator.