A process for producing a substituted metallocene compound comprises reacting a first compound with a transfer-agent, wherein the first compound comprises a complex of a transition metal atom selected from Group 3, 4, 5 or 6 of the Periodic Table of Elements, or a lanthanide metal atom, or actinide metal atom and at least one monocyclic or polycyclic ligand that is pi-bonded to M and is substituted with at least one halogen or sulfonate substituent and the transfer-agent comprises a hydrocarbyl, substituted hydrocarbyl, halocarbyl, substituted halocarbyl, silylcarbyl, or germylcarbyl radical capable of replacing said at least one halogen or sulfonate substituent of said first compound under reaction conditions.