Accelerating Ni(II) precatalyst initiation using reactive ligands and its impact on chain-growth polymerizations

Nickel(II) complexes with varying reactive ligands, which were designed to selectively accelerate the initiation rate without influencing the propagation rate in the chain-growth polymerization of π-conjugated monomers, were investigated. Precatalysts with electronically varied reacting groups led to faster initiation rates and narrower molecular weight distributions. Computational studies revealed that the reductive elimination rates are largely modulated by the ability of the two reacting arenes to stabilize the increasing electron density on the catalyst during reductive elimination. Overall, these studies provide insight into a key mechanistic step of cross-coupling reactions (reductive elimination) and highlight the importance of initiation in controlled chain-growth polymerizations.