A composition comprising a solid methyl aluminoxane support material and compound of the formula (I) shown below: wherein R 1 and R 2 are each independently hydrogen or linear (1-4C)alkyl, or R 1 and R 2 are linked such that, when taken in combination with the atoms to which they are attached, they form a 6-membered fused aromatic ring optionally substituted with one or more groups selected from (1-6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1-6C)alkoxy, aryl, heteroaryl, carbocyclic and heterocyclic, wherein each aryl, heteroaryl, carbocyclic and heterocyclic group is optionally substituted with one or more groups selected from (1-6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1-6C)alkoxy, halo, amino, nitro, cyano, (1-6C)alkylamino, [(1-6C)alkyl] 2 amino and -S(O) 2 (1-6C)alkyl; R 3 and R 4 are each independently hydrogen or linear (1-4C)alkyl, or R 3 and R 4 are linked such that, when taken in combination with the atoms to which they are attached, they form a 6-membered fused aromatic ring optionally substituted with one or more groups selected from (1-6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1-6C)alkoxy, aryl, heteroaryl, carbocyclic and heterocyclic, wherein each aryl, heteroaryl, carbocyclic and heterocyclic group is optionally substituted with one or more groups selected from (1-6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1-6C)alkoxy, halo, amino, nitro, cyano, (1-6C)alkylamino, [(1-6C)alkyl] 2 amino and -S(O) 2 (1-6C)alkyl; R 5 is hydrogen or linear (1-4C)alkyl; X is selected from zirconium or hafnium; and Y is selected from halo, hydride, a phosphonated, sulfonated or borate anion, or a (1-6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1-6C)alkoxy, -C(O)NR a R b , NR a R b , aryl or aryloxy group which is optionally substituted with one or more groups selected from halo, (1-4C)alkyl, nitro, NR a R b , phenyl, (1-6C)alkoxy, - C(O)NR a R b , or Si[(1-4C)alkyl] 3 ; wherein R a and R b are independently hydrogen or (1-4C)alkyl. R 1 and R 2 are each independently hydrogen or linear (1-4C)alkyl, or R 1 and R 2 are linked such that, when taken in combination with the atoms to which they are attached, they form a 6-membered fused aromatic ring optionally substituted with one or more groups selected from (1-6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1-6C)alkoxy, aryl, heteroaryl, carbocyclic and heterocyclic, wherein each aryl, heteroaryl, carbocyclic and heterocyclic group is optionally substituted with one or more groups selected from (1-6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1-6C)alkoxy, halo, amino, nitro, cyano, (1-6C)alkylamino, [(1-6C)alkyl] 2 amino and -S(O) 2 (1-6C)alkyl; R 3 and R 4 are each independently hydrogen or linear (1-4C)alkyl, or R 3 and R 4 are linked such that, when taken in combination with the atoms to which they are attached, they form a 6-membered fused aromatic ring optionally substituted with one or more groups selected from (1-6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1-6C)alkoxy, aryl, heteroaryl, carbocyclic and heterocyclic, wherein each aryl, heteroaryl, carbocyclic and heterocyclic group is optionally substituted with one or more groups selected from (1-6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1-6C)alkoxy, halo, amino, nitro, cyano, (1-6C)alkylamino, [(1-6C)alkyl] 2 amino and -S(O) 2 (1-6C)alkyl; R 5 is hydrogen or linear (1-4C)alkyl; X is selected from zirconium or hafnium; and Y is selected from halo, hydride, a phosphonated, sulfonated or borate anion, or a (1-6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1-6C)alkoxy, -C(O)NR a R b , NR a R b , aryl or aryloxy group which is optionally substituted with one or more groups selected from halo, (1-4C)alkyl, nitro, NR a R b , phenyl, (1-6C)alkoxy, - C(O)NR a R b , or Si[(1-4C)alkyl] 3 ; wherein R a and R b are independently hydrogen or (1-4C)alkyl. <EOS>