Switchable living nickel(ii) α-diimine catalyst for ethylene polymerisation.

Design and synthesis of a Ni(ii) "sandwich" α-diimine complex (1) resulted in a switchable catalyst for the living polymerisation of ethylene over a range of temperatures and pressures. Varying these conditions produced a well-defined tetrablock copolymer comprising branched and highly linear polyethylenes. This copolymer improved the toughness of a phase separated LDPE/HDPE blend by nonreactive interfacial compatibilisation.

Synthesis of Semicrystalline Polyolefin Materials: Precision Methyl Branching via Stereoretentive Chain Walking.

We report the discovery of C-symmetric nickel catalysts capable of the regio- and isoselective polymerization of 1-butene to produce isotactic 4,2-poly(1-butene), a new semi-crystalline polyolefin. The catalyst exhibits enantioface selectivities as high as 84% and the resulting polymers display melting temperatures up to 86 °C. This system marks a rare example of preserving stereochemistry through a chain walking polymerization process.