Alkaline earth metal complexes of a chiral polyether as initiator for the ring-opening polymerization of lactide.

A chiral, tetradentate polyether ligand with a trans-1,2-cyclohexanediyl backbone, bis(methoxyethoxy)-trans-1,2-cyclohexane (5), was synthesized as both a racemate and the (S,S) enantiomer. 5 was found to form stable adducts with alkaline earth metal amides [M{N(SiMe(3))(2)}(2)(thf)(x)] (M = Mg (x = 0), Ca (x = 2) and Sr (x = 2/3)), [Ca{N(SiHMe(2))(2)}(2)(thf)] as well as with hydrocarbyl compounds [Mg(CH(2)SiMe(3))(2)] and [Ca(η(3)-C(3)H(5))(2)]. X-ray diffraction study of the bis(amide) [((S,S)-)Ca{N(SiMe(3))(2)}(2)] and of the bis(allyl) [(rac-5)Ca(η(3)-C(3)H(5))(2)] was performed. The complexes obtained were tested as initiators for the ring-opening polymerization of meso-, racemic and L-lactide.