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] = C6H11NCHCHNC6H11; 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.

Graphical abstractα-Diimine nickel complexes have been synthesized and evaluated in the atom transfer radical polymerization of styrene. Nickel chloride derivatives are ineffective at controlling the polymerization due to low solubility, while the corresponding nickel bromide catalysts, in conjunction with 1-PEBr, afford well-controlled polymerizations.Figure optionsDownload full-size imageDownload as PowerPoint slide