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 β-diketiminate ligand were synthesized for the first time. The mixed-ligand ytterbium chlorides (CH3C5H4)[(DIPPh)2nacnac]YbCl (1), (C9H7)[(DIPPh)2nacnac]YbCl (2), and (ArO)[(DIPPh)2nacnac]YbCl(THF) (3) ((DIPPh)2nacnac = N,N-diisopropylphenyl-2, 4-pentanediimine anion, ArO = 2,6-di-tert-butyl-4-methylphenoxo), which were obtained in high yield by using [(DIPPh)2nacnac]YbCl2(THF)2 as precursor, were reduced by Na/K alloy in THF to afford the corresponding divalent species (CH3C5H4)[(DIPPh)2nacnac]Yb(THF) (4), (C9H7)[(DIPPh)2nacnac]Yb(THF) (5), and {(ArO)[(DIPPh)2nacnac]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.