Synthesis and characterization of β-diketiminate lanthanide complexes: the effect of the bulkiness of ancillary ligand on the reaction

The reactions of ytterbium dichlorides with different β-diketiminate ligand ((Ar)NC(Me)CHC(Me)N(Ar′), Ar=Ar′=C6H5 (L1); Ar=Ar′=2,6-Me2&z.sbnd;C6H3 (L2); Ar=C6H5, <f>Ar′=2,6-Pr2i-C6H3 (L3)</f>) with 1 equiv of Cp′Na were studied. It was found that the bulkiness of β-diketiminate ligand and cyclopentadienyl group both have significant effect on the above reaction. For less bulky ligands L1 and L2, the reaction affords not the expected mixed-ligand ytterbium chloride, (C5H5)YbLCl or (CH3C5H4)YbCl, but the ligand-redistributed product (C5H5)2YbL or (CH3C5H4)2YbL. For bulkier ligand L3, the desired anionic ytterbium chloride (C5H5)YbL3(μ-Cl)2Li(THF)2 is obtained. For the smallest ligand L1, the expected ytterbium monochloride can also be obtained using bulky C5Me5Na as reactant. Each of these complexes was well characterized, while several have been characterized by X-ray diffraction structure determination. [Copyright &y& Elsevier]