Synthesis and molecular structure of the cationic samarium phenoxide complex [(ArO)2Sm(DME)2][BPh4] · THF and its catalytic activity for the polymerization of ε-caprolactone

The first cationic samarium phenoxide complex, [(ArO)2Sm(DME)2][BPh4] · THF (ArO = 2,6-di-tert-butyl-4-metyl-phenoxide) (1), has been synthesized by one-electron oxidation reaction of (ArO)2Sm(THF)3 with AgBPh4 in high yield and structurally characterized. The complex 1 can be used as a single-component catalyst for the ring-opening polymerization of ε-caprolactone (ε-CL) with high activity. The activity of the complex 1 is much higher than that of the parent neutral complex (ArO)3Sm(THF)2, and is comparable to that of the divalent complex (ArO)2Sm(THF)3. A coordination-insertion polymerization mechanism was supposed according to the end-group analysis.