New bulky allyl complexes of lanthanide metals: role of alkali-metal cations in controlling solid-state and solution assemblies in precatalysts

The reaction of the bulky allyl anion [1,3-C3H3(SiMe3)2]- with SmI2(THF)2 gives the allyl-bridged dimer [Sm(C3H3(SiMe3)2)3{μ-K(THF)2}]2, the first structurally authenticated Sm(II) allyl complex. The compound is a highly effective single-component catalyst for the polymerization of methyl methacrylate and ε-caprolactone.