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 MgnBu₂ afforded the homoleptic complex nacnac(Bn)₂Mg. 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 °C afforded polylactide with a small isotactic bias (P(m) = 0.52, and 0.55, respectively).