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. The preparation of ten lanthanide complexes bearing para‐toluene sulfonamide ligands were obtained by the reaction of Ln[N(TMS)2]3 (Ln = La, Gd) with para‐toluene sulfonamides is described. The crystal structure of Complex 3 was determined and discussed. 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.