Bimetallic Al(III) Compounds as Catalysts for the Synthesis of Biodegradable Polyesters and Polycarbonates

Ethylenediamine bridged benzoxazine proligands were synthesized by a modified Mannich condensation reaction. The reaction of the proligands with two equivalents of AlMe3 resulted in the formation of dinuclear Al(III) compounds in high yield and purity. When the ligand binds to the Al(III) center, it forms two separate six-membered N,O-chelates with the two Al atoms that resembles the N-alkylated salan moiety. Each aluminum atom adopts a distorted tetrahedral geometry as revealed from the single-crystal X-ray diffraction studies of 1. The catalytic activity of these aluminum compounds was investigated towards the ROP of rac-LA and ROCOP of epoxides (PO, CHO, tBuGE) and phthalic anhydride and ROCOP of CHO with CO2. These aluminum compounds showed notable catalytic activity towards the ROP and ROCOP reactions in the absence of cocatalyst.