A metal complex of the formula (1) CyAMX(L)n  (1) wherein Cy is a cyclopentadienyl-type ligand, M is a metal of group 4; A is an amidine-containing ligand moiety, represented by formula 2: wherein the amidine-containing ligand is covalently bonded to the metal M via the imine nitrogen atom, and Sub1 is a substituent comprising a group 14 atom through which Sub1 is bonded to the imine carbon atom and Sub2 is a substituent comprising a heteroatom of group 15, through which Sub2 is bonded to the imine carbon atom; X is an allyl borate ligand derived from a conjugated diene ligand, D, and a borane, B and L is a neutral Lewis basic ligand wherein the number of said metal ligands “n” is in the range of 1 to the amount that specifies the 18-electron rule.