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 ((BDICF3-I)H = [CH­(CCF3N­C6H4-2,6-CH­(CH3)2)2]; (BDICF3-II)H = [CH­(CCF3N­C6H4-2,6-C2H5)2],
and (BDICF3-III)H = [CH­(CCF3N­C6H4-2,6-CH3)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 BDICF3-II-ZnEt and BDICF3-III-ZnEt are active
initiators for the polymerization of (rac)-lactide
(LA).