Transition metal complexes of triphosphorus macrocycles: A new class of homogeneous olefin polymerisation catalysts

Some early transition metal (Ti, V, Cr) complexes of the triphosphorus macrocycle 1,5,9-triethyl-1,5,9-triphosphacyclododecane, [12]aneP3Et3, and related derivatives [12]aneP3R3 (R = Ph, C3H6OMe) have been examined for their reactivity towards ethene and propene. All complexes of the type [12]aneP3Et3MCl3 display moderate catalytic activity in the homogeneous polymerisation of ethene when combined with an alkyl aluminium co-catalyst to give very high molecular weight polymers. Preliminary activation of chromium complexes with alkylating agents was also studied but these were inactive in the absence of a co-catalyst. Substitution of the P-borne alkyl group with a pendant ether function was found to switch the catalytic activity of chromium() complexes from polymerisation to oligomerisation. A nickel halide complex of [12]aneP3Et3 was also found to be active in alkene polymerisation.