Synthesis and structural characterization of divalent ytterbium complexes supported by β-diketiminate ligands and their catalytic activity for the polymerization of methyl methacrylate

Three divalent ytterbium complexes supported by a beta-diketiminate ligand were synthesized for the first time. The mixed-ligand ytterbium chlorides (CH3C5H4)[(DIPPh)(2)nacnac]YbCl (1), (C9H7)[(DIPPh)(2)nacnac]YbCl (2), and (ArO)[(DIPPh)(2)nacnac]YbCl(THF) (3) ((DIPPh)(2)nacnac = N,N-dilsopropylphenyl-2, 4-pentanediimine anion, ArO = 2,6-di-tert-butyl-4-methylphenoxo), which were obtained in high yield by using [(DIPPh)(2)nacnac]YbCl2(THF)(2) as precursor, were reduced by Na/K alloy in THF to afford the corresponding divalent species (CH3C5H4)[(DIPPh)(2)nacnac]Yb(THF) (4), (C9H7)[(DIPPh)(2)nacnac]Yb(THF) (5), and {(ArO)-[(DIPPh)(2)nacnac]Yb(THF)}(THF) (6), respectively. Complexes 2-6 were well characterized, and crystal structures of complexes 4-6 were determined. These divalent complexes exhibit good catalytic activity for the polymerization of methyl methacrylate.