Development of an Alpha-Diimine Aluminum Catalyst for Atom Transfer Radical Polymerization

Aluminum is an attractive metal in developing novel homogeneous catalysts due to its natural abundance, low cost, and benign environmental impact. The Graves group has been investigating its chemistry by developing metal complexes with redox non-innocent ligands. Thus, the previously reported (LMes 2- )AlCl(THF) (LMes = N,N′-bis[2,4,6-trimethylphenyl]-2,3-dimethyl-1,4-diazabutadiene) will be investigated as a potential atom transfer radical polymerization (ATRP) catalyst. Using gel permeation chromatography and 1H-NMR spectroscopy, this study investigates a model ATRP system of methyl methacrylate (MMA) with (LMes2- )AlCl(THF). The dependence of polymerization outcomes on several reaction parameters was tested. In addition, a time-resolved polymerization study determined that (LMes 2- )AlCl(THF) does catalyze a living ATRP process, but undergoes slow initiation kinetics.