Monomeric metal alkoxides and trialkyl siloxides: (BDI)Mg((OBu)-Bu-t)(THF) and (BDI)Zn(OSiPh3)(THF). Comments on single site catalysts for ring-opening polymerization of lactides

The monomeric alkoxide (BDI)Mg((OBu)-Bu-t)(THF) and triphenylsiloxide (BDI)Zn(OSiPh3)(THF) have been prepared and characterized and shown to reversibly dissociate THF in solution on the NMR time scale; both compounds are active precursors for the ring-opening polymerization of lactide and the rate of polymerization is notably faster for the magnesium complex though in the polymerization of rac-lactide only the zinc complex shows selectivity for heterotactic tetrads.