Synthesis, structures and ε-caprolactone polymerization activity of aluminum N,N′-dimethyloxalamidates

Alkyl aluminum N,N′-dimethyloxalamidates R4Al2(dmoa) (1, R = Me; 2, R = Et; 3, R = iBu; 4, R = tBu) (dmoa-H2 = N,N′-dimethyloxalamide) have been prepared and characterized. Molecular structures of the compounds 1 and 4 have been determined by X-ray crystallography. The centrosymmetric molecules of the compounds consist of one N,N′-dimethyloxalamidate unit bonded to two four-coordinated aluminum atoms. Each of the aluminum atoms is bonded to two alkyl groups, and oxygen and nitrogen atoms originating from two different amidate groups. A skeleton framework of the molecules of 1 and 4 consists of two fused AlNOC2 heterocyclic rings, which are flat and positioned in one plane. It was shown that compounds 1–3 were initiators in a process of ring opening polymerization (ROP) of ε-caprolactone. The compound 4 exhibited low activity in ROP.