Catalysts

A complex comprising a ligand of formula (I):

• wherein
• each R1, which may be the same or different, is hydrogen, an optionally substituted C1-20 hydrocarbyl group, N(R5)2, silyl, siloxy;
• an optionally substituted heteroaryl group, an optionally substituted heterocyclyl group or two R1 groups on adjacent carbon atoms taken together to form an optionally substituted 5- to 8-membered fused ring;
• each R2, which may be the same or different is hydrogen, is hydrogen, an optionally substituted C1-20 hydrocarbyl group, N(R5)2, silyl, siloxy;
• an optionally substituted heteroaryl group, or an optionally substituted heterocyclyl group;
• R3, which binds the 5-membered ring of the top ligand and to the 6-membered ring of the indenyl group, is —(Si(R5)2)p—, where p is 1 or 2, —(C(R5)2)n— where n is an integer of 2 or more;
• each R4 which are the same or different, is hydrogen, an optionally substituted C1-20 hydrocarbyl group, N(R5)2, silyl, siloxy, an optionally substituted heteroaryl group, an optionally substituted heterocyclyl group or two R4 groups on adjacent carbon atoms taken together form an optionally substituted 5- to 8-membered fused carbon ring;
• each R5, which are the same or different, is hydrogen, an optionally substituted C1-20 hydrocarbyl group, or two R5 groups taken together form an optionally substituted 5- to 8-membered ring;
• a is 0 to 3;
• b is 0 to 3
• c is 0 to 4;
• complexed to a metal ion, M.