Ring-Opening Polymerization Reactions of -Caprolactone and Lactides Initiated by (Benzimidazolylmethyl)amino Magnesium(ii) Alkoxides

Reactions of (benzimidazolylmethyl)amine ligands N-((1H-benzo[s]imidazol-2-yl)methyl)-2,6-dimethylaniline (L1), N-((1H-benzo[d]imidazol-2-yl)methyl)-2,6-diisopropylaniline (L2), and N-((1H-benzo[d]imidazol-2-yl)methyl)-2,4,6-trimethylaniline (L3) with Mg(Bu-n)(2) in the presence of either benzyl alcohol (BnOH) or tert-butyl alcohol (t-BuOH) afforded the respective Mg-II alkoxides [Mg(L1)(OBn)](2) (1), [(Mg(L2)(OBn)](2) (2), [Mg(L3)(OBn)](2) (3), [Mg(L2)(t-BuO)](2) (4). Complexes 1-4 formed efficient catalysts for the ring-opening polymerization (ROP) of -caprolactone (-CL), d,l-lactide (d,l-LA) and l-lactide (l-LA) at 110 degrees C. The catalytic activities of these complexes in the ROP reactions were influenced by the steric effect of the ligands. Kinetic studies showed pseudo-first-order dependency on monomer. Polycaprolactone and polylactides of moderate weight-average molecular weights of 15285 and 5200gmol(-1) and fairly narrow polydispersity indexes from 1.24 to 1.58 were produced.