Synthesis and Structural Characterization of Divalent Ytterbium Complexes Supported byβ-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 (CH 3 C 5 H 4 )[(DIPPh) 2 nacnac]YbCl ( 1 ), (C 9 H 7 )[(DIPPh) 2 nacnac]YbCl ( 2 ), and (ArO)[(DIPPh) 2 nacnac]YbCl(THF) ( 3 ) ((DIPPh) 2 nacnac = N, N -diisopropylphenyl-2, 4-pentanediimine anion, ArO = 2,6-di- tert -butyl-4-methylphenoxo), which were obtained in high yield by using [(DIPPh) 2 nacnac]YbCl 2 (THF) 2 as precursor, were reduced by Na/K alloy in THF to afford the corresponding divalent species (CH 3 C 5 H 4 )[(DIPPh) 2 nacnac]Yb(THF) ( 4 ), (C 9 H 7 )[(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.