Organolanthanides with 3-(2-pyridylmethyl) indenyl ligands: synthesis, crystal structures and catalytic activities of divalent complexes for ε-caprolactone polymerization

Reaction of 3-(2-pyridylmethyl)indenyl lithium (1) with LnI2(THF)2 (Ln = Sm, Yb) in THF produced the divalent organolanthanides (C5H4NCH2C9H6)2LnII(THF) (Ln = Sm (2), Yb (3)) in high yield. 1 reacts with LnCl3 (Ln = Nd, Sm, Yb) in THF to give bis(3-(2-pyridylmethyl)indenyl) lanthanide chlorides (C5H4NCH2C9H6)2LnIIICl (Ln = Nd (4), Sm (5)) and the unexpected divalent lanthanides 3 (Ln = Yb). Complexes 2–5 show more stable in air than the non-functionalized analogues. X-ray structural analyses of 2–4 were performed. 2 and 3 belong to the high symmetrical space group (Cmcm) with the same structures, they are THF-solvated 9-coordinate monomeric in the solid state, while 4 is an unsolvated 9-coordinate monomer with a trans arrangement of both the sidearms and indenyl rings in the solid state. Additionally, 2 and 3 show moderate polymerization activities for ε-caprolactone (CL).