(RO)₂Ta[tris(2-oxy-3,5-dimethylbenzyl)amine]: Structure and Lactide Polymerization Activities

The novel atrane-like six-coordinate (RO)2TaL complexes [where R = Me or Et and L = tris(2-oxy-3,5-dimethylbenzyl)amine] containing three six-membered rings have been synthesized and characterized. The R = Me complex is the first group 5 representative of this class of compounds structurally characterized by X-ray means. Somewhat surprisingly, these compounds failed to function as single-site initiators for the polymerization of l-LA to isotactic PLA and rac-LA to atactic PLA, whereas Ta(OEt)5 and two titanium analogues ROTiL (where R = 2,6-di-i-PrC6H3 and i-Pr) as well as Ti(O-i-Pr)4 were effective catalysts for both polymerizations.