Nacnac(Bn)MgOtBu: a diketiminate-based catalyst for the polymerisation of rac-lactide with slight isotactic preference

The reaction of N,N'-dibenzyl-2-amino-4-imino-pent-2-ene, nacnac(Bn)H, with 1 or 2 equiv. of MgnBu(2) afforded the homoleptic complex nacnac(2)(Bn)Mg. The reaction of nacnac(Bn)H with Mg(N(SiMe3)(2))(2) yielded nacnac(Bn)MgN(SiMe3)(2), which reacted with tert-butanol to form nacnac(Bn)MgOtBu. The latter complex crystallizes as an alkoxide bridge dimer and is active in the ring-opening polymerisation of rac-lactide. Polymerisations at room temperature afforded atactic polylactide, while polymerisations at -17 and -26 degrees C afforded polylactide with a small isotactic bias (P-m = 0.52, and 0.55, respectively).