Novel Titanatranes with Different Ring Sizes: Syntheses, Structures, and Lactide Polymerization Catalytic Capabilities

Abstract

The new titanatranes (Ar = 2,6-di-i-Pr-phenoxy; Ar‘ = 2,4-di-MeC6H2; x = 0, 5; x = 1, 6; x = 2, 7; x = 3, 8) featuring three six-membered chelating rings (5) to three five-membered chelating rings (8) in a stepwise fashion through 6 and 7 were synthesized from the corresponding trihydroxy chelating ligands 1−4, respectively, using an equimolar mixture of Ti(O-i-Pr)4 and 2,6-di-i-Pr-phenol. The molecular structures of 5 and 6, determined by X-ray means, revealed that in both of these complexes the transannular N−Ti bond lengths [2.305(2) Å, 5; 2.287(4) Å, 6] are at the short end of the range for titanatranes possessing three five-membered rings. These compounds show good catalytic activity for the bulk homopolymerization of l- and rac-lactide at 130 °C.