Synthesis and structure characterization of bis- and mono(amidate) lanthanide (Ln = La, Gd) complexes and their application in the polymerization of ε-caprolactone

Abstract

A serious of bis- and mono(amidae) lanthanide complexes 1–10 were prepared by amine elimination of amide (R′(HNCO)R) with 1 equiv of Ln[N(SiMe3)2]3 (Ln = La: 1, R = Ph, R′ = tBu; 2, R = Ph, R′ = iPr; 3, R = iPr, R′ = iPr; 4, R = iPr, R′ = tBu), or 0.5 M equiv of Ln[N(SiMe3)2]3 (Ln = La: 5, R = tBu, R′ = tBu; 6, R = tBu, R′ = iPr; 7, R = iPr, R′ = iPr; 8, R = iPr, R′ = tBu; Ln = Gd: 9, R = iPr, R′ = iPr; 10, R = Ph, R′ = iPr). Complexes 2, 5, 6, 7, 8a, 9 and 10 have been characterized by X-ray crystal structural analysis. The structures reveal that all these complexes are analogous binuclear via two bridging amidate ligands, built around a planar Ln2O2 ring. The catalytic properties of complexes 1, 2, 3, 5, 7, 9 and 10 on the ring-opening polymerization (ROP) of ε-caprolactone have been studied. The results show those complexes are efficient catalysts for the ring-opening polymerization of ε-caprolactone.