[N-[2,6-Bis(1-methylethyl)phenyl]-α-[2-(1-methylethyl)phenyl]-6-(1-naphthalenyl-κC2)-2-pyridinemethanaminato(2-)-κN1,κN2]dimethylhafnium is a catalyst used in chain shuttling polymerization reactions and other related reactions involving block copolymers.