Structural Diversity and Multielectron Reduction Reactivity of Samarium(II) Iodido-β-diketiminate Complexes Dependent on Tetrahydrofuran Content

The molecular structures of complexes [Sm(Nacnac)I(thf)n] (Nacnac = HC(C(Me)Ndipp)2-, dipp = 2,6-diisopropylphenyl, thf = tetrahydrofuran) depending on the number of thf ligands are studied. The complete removal of thf from a known complex [Sm(Nacnac)I(thf)2] leads to a tetranuclear product [Sm(Nacnac)I]4 (4). The partial removal of thf results in mixtures of dinuclear [Sm2(Nacnac)2I2(thf)] (2), trinuclear [Sm3(Nacnac)3I3(thf)] (3), and tetranuclear [Sm4(Nacnac)4I4(thf)2] (4*) complexes and 4, depending on the conditions. The reaction of solvent-free SmI2 with 1 equiv of K(Nacnac) results mainly in [Sm(Nacnac)2] (1), while the interaction of 4 with certain amounts of thf allows obtaining pure 2 and 3 (with the admixture of 4*). Complex 4* is the exact dimer of 2, and both compounds are stable in solutions. Reactions with 3 and 4 as reductants are studied. 4 is oxidized by I2 to stoichiometrically yield two products, mixed-valent tetranuclear [Sm4(Nacnac)4I5] (5) and binuclear [Sm(Nacnac)I2]2 (6) complexes. In the reaction of 4 with nBu3PTe, a trinuclear complex [Sm3(Nacnac)3(μ-I)3(μ3-E)2] (8, E = I or Te) is formed in small amounts, with the formation of 6 as the second product. 3 serves as a two-electron reductant in the reaction with nBu3PTe to yield a trinuclear complex [Sm3(Nacnac)3I3(μ-Te2)] (7). Complexes 2, 4, 4*, 5, 6, and 8 possess a unique flat SmxIy core of heavy atoms, which is assumed to be a consequence of the Nacnac ligand geometry.