Synthesis and structure of para‐toluene sulfonamide lanthanide complexes and their application in the polymerization of ε‐caprolactone.

A series of para-toluene sulfonamide ligands [TsNHPr-i(HL1), TsNHBu-t(HL2), TsNHPh(HL3), TsNHPhMe-p(HL4), TsNHPhOMe-p(HL5)] were synthesized by amidation using para-toluene sulfonyl chloride reacting with different primary amines. A series of homoleptic lanthanide complexes (Ln L3, 1–10) (Ln = La, L = L1 (1), Ln = Gd, L = L2 (2), Ln = La, L = L2 (3), Ln = Gd, L = L2(4), Ln = La, L = L3 (5), Ln = Gd, L = L3 (6), Ln = La, L = L4 (7), Ln = Gd, L = L4(8), Ln = La, L = L5 (9), Ln = Gd, L = L5 (10)) were prepared by amine elimination reactions of the ligands with Ln[N(SiMe3)2]3 (Ln = La, Gd). Complexes 1, 3, 5, 7 and 9 were all characterized by NMR spectra, and the structures of complex 3 was determined by single-crystal X-ray diffraction. Complex 3 crystallizes a binuclear cluster, consisting of two La3+ and six (TsNBu-t)− anions. Three (TsNBu-t)− anions are chelating to each La3+ as bidentate model with O and N forming three-membered chelate rings; one of three anions is bridging to another La3+ via oxygen. All complexes were characterized using elemental analysis and infrared spectra. The catalytic properties of complexes 1–10 for the ring-opening polymerization of ε-caprolactone were studied and the results showed that all complexes are efficient initiators for this ring-opening polymerization reaction. [ABSTRACT FROM AUTHOR]