Aspects of transition metal mediated polymerizations

Catalysts based on metallocene complexes of early transition metals herald a new era in Ziegler-Natta olefin polymerization. The developments are driven primarily by the flexibility and high activity of metallocene catalysts, which allow excellent control of polymer properties and have led to a remarkably wide spectrum of polymers and copolymers. In-depth mechanistic understanding is proving crucial for catalyst design and has opened up the use of metallocenes in non-Ziegler chemistry, notably as initiators for carbocationic polymerizations. Recently developed late transition metal complexes have substantially added to the range of olefin (co)polymers that are now accessible, including copolymerizations with carbon monoxide and polar monomers.