Ring opening homo- and copolymerization of lactide (LA) and ε-caprolactone (ε-CL) in solution with several Ga catalysts yielded isotactic-enriched PLAs and well defined diblock copolymers by coordination insertion mechanism (CIM).

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LGa {L = HC[C(Me)N(2,6- iPrCH)]} reversibly reacts with EPh (E = Sb, Bi) in a temperature-dependent equilibrium reaction with insertion into the E-E bond and formation of LGa(EPh) (E = Sb 1, Bi 2). Analogous findings were observed in the reactions of LGa {L = (CH)NC[N(2,6- iPrCH)]} with ER (R = Ph, Et), yielding LGa(EPh) (E = Sb 3, Bi 4) and LGa(EEt) (E = Sb 5, Bi 6). 1-3 and 5 were isolated by fractional crystallization at low temperature, whereas 4 and 6 could not be isolated in their pure form even at low temperature. In contrast, reactions of [Cp*Al] (Cp* = CMe) with SbR (R = Ph, Et) and BiEt did not proceed with insertion into the E-E bonds but with formation of (Cp*Al)E (E = Sb, 7; Bi, 8), whereas the reaction with BiPh yielded metallic bismuth. 8 was also formed in the reaction of [Cp*Al] and BiEt at ambient temperature, whereas the analogous reaction of [Cp*Al] with SbEt did not yield 7 even under drastic reaction conditions (120 °C, 3 days). In contrast, Cp*Ga and SbR (R = Ph, Et) were found to react only at elevated temperature (120 °C) with formation of antimony metal.

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