Nickel(II) α-diimine catalysts for the atom transfer radical polymerization of styrene

The synthesis and evaluation of Cy[N,N]NiX2 complexes (where Cy[N,N] = C6H11single bondNdouble bond; length as m-dashCHsingle bondCHdouble bond; length as m-dashNsingle bondC6H11; X = Cl, Br) as catalysts for atom transfer radical polymerization are reported. Cy[N,N]NiCl2 offers poor control over the polymerization of MMA and styrene due to catalyst insolubility. The more soluble bromo catalyst Cy[N,N]NiBr2, promotes rapid styrene polymerization, but with inefficient initiation, affording higher than expected molecular weights based on [M]o/[I]o ratios. Utilizing 1-PEBr results in efficient initiation to give low polydispersities (Mw/Mn ∼ 1.2) and polystyrene molecular weights that correlate with monomer:initiator ratios.