A multimetallic iron(ii)–lithium complex as a catalyst for ε-caprolactone polymerization

Abstract

Treatment of the lithium salt of β-ketimine with FeCl₂(THF)_1.5 in the presence of LiN(SiMe₃)₂ and water affords the multimetallic iron(II)–lithium complex 1, [(L^Me)₂Fe]₃Li₂O [where L^Me = MeC(O)CHC(NMe)Me]. In complex 1 three separated (L^Me)₂Fe units are bound together by one Li₂O species, which leads to the formation of an interesting {Fe₃Li₂O} core structure. Complex 1 can be used as a single-component initiator for the ring-opening polymerization of ε-caprolactone at room temperature, achieving a monomer conversion of 98% within 100 min, and a narrow molecular weight distribution (PDI = 1.28) of the resulting polymer.