Zinc compounds with or without Zn-Zn bond: Alkali metal reduction of LZnCl2 (L = alpha-diimine ligands)

A series of mononuclear and dinuclear zinc compounds, [Na(Et2O)](2)[(L-H(iPr))Zn-Zn(L-H(iPr))]center dot Et2O (1), [Zn-2(L-H(iPr))(3)K-2(Et2O)(2)](n) (2, L-H(iPr) = [(2,6-(Pr2C6H3)-Pr-i)NCH](2)), [Zn(L-H(Mes))(2)] (4, L-H(Mes) = [(2,4,6-Me3C6H2)NCH](2)), and [ZnLMes Na-2(2)(THF)(2)] (5, L-Mes = [(2,4,6-Me3C6H2)NC(Me)](2)), and a potassium complex, [(L-H(iPr))(2)K-4(THF)(2)](n) (3), have been synthesized by alkali metal reduction of the corresponding LZnCl2 precursors. The Zn-Zn bond in 1 (2.3673(6) angstrom) is slightly shorter than that in the analogous compounds [M(THF)(2)](2)[(LZn)-Zn-iPr-ZnLiPr](L-iPr = [(2,6-(Pr2C6H3)-Pr-i)NC(Me)](2), M = Na, 2.399(1) angstrom; M = K, 2.393(1) angstrom). Complexes 2 and 3 feature a two-and one-dimensional (linear chain) polymeric structure, respectively, linked by K-C bonds between the potassium ion and aryl carbon atoms. Notably, complex 2 contains a ligand whose central C2N2 core is in the trans conformation, acting as a non-chelating bridge between the two zinc atoms. While the ligands in 1, 2, 3 and 5 are doubly reduced to the dianion, complex 4 contains a pair of monoanionic ligands.