Synthesis of Lewis Acidic, Aromatic Aminotroponiminate Zinc Complexes for the Ring-Opening Polymerization of Cyclic Esters.

Three novel aminotroponiminate (ATI) zinc complexes I-III (I = [(Ph)ATI]Zn-N(SiMe), II = [(CH-2,6-CH/Ph)ATI]Zn-N(SiMe), and III = [(CH-2,6-CH(CH)/Ph)ATI]Zn-N(SiMe)) were synthesized and tested in the ring-opening polymerization of the lactones β- rac-butyrolactone (BBL) and rac-lactide (LA). The ligands, with two of them literature unknown, were readily obtained via a three-step synthesis from tropolone. Forming a five-membered metallacycle with zinc, the complexes were further structurally examined via single-crystal X-ray analysis and compared with that of the established, 6-ringed β-diiminate (BDI) complex IV ([CH(CMeNPh)]Zn-N(SiMe)).