NacnacBnMgOtBu: a diketiminate-based catalyst for the polymerisation of rac-lactide with slight isotactic preference

Abstract

The reaction of N,N′-dibenzyl-2-amino-4-imino-pent-2-ene, nacnac^BnH, with 1 or 2 equiv. of MgnBu₂ afforded the homoleptic complex nacnac^Bn₂Mg. The reaction of nacnac^BnH with Mg(N(SiMe₃)₂)₂ yielded nacnac^BnMgN(SiMe₃)₂, which reacted with tert-butanol to form nacnac^BnMgOtBu. 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).