Electron-Deficient β-Diiminato-Zinc-Ethyl Complexes: Synthesis, Structure, and Reactivity in Ring-Opening Polymerization of Lactones

A series of β-diiminato zinc(II) complexes bearing two electron-withdrawing trifluoromethyl groups in the pentane ligand backbone were successfully isolated ((BDI CF 3 -I)H = [CH(CCF 3 NC 6 H 4 -2,6-CH(CH 3 ) 2 ) 2 ]; (BDI CF 3 -II)H = [CH(CCF 3 NC 6 H 4 -2,6-C 2 H 5 ) 2 ], and (BDI CF 3 -III)H = [CH(CCF 3 NC 6 H 4 -2,6-CH 3 ) 2 ]). The solid-state structures illustrate differences in the ligation of the Zn atom compared to a literature known BDI-ZnEt complex. All catalysts show good activities in the ring-opening polymerization of the cyclic ester ( rac )-β-butyrolactone (BL), whereas only BDI CF 3 -II-ZnEt and BDI CF 3 -III-ZnEt are active initiators for the polymerization of ( rac )-lactide (LA).