Zinc compounds with or without Zn_Zn bond: Alkali metal reduction of LZnCl_2 (L = α-diimine ligands)

摘要

A series of mononuclear and dinuclear zinc compounds, [Na(Et_2O)]_2[(~HL~(iPr))Zn_Zn(~HL~(iPr))]_Et_2O (1), [Zn_2(~HL~(iPr))_3K_2(Et_2O)_2]_n (2, ~HL~(iPr) = [(2,6-~iPr_2C_6H_3)NCH]_2), [Zn(~HL~(Mes))_2] (4,~HL~(Mes)= [(2,4,6-Me_3C_6H_2)NCH]_2), and [ZnL~(Mes)_2Na_2(THF)_2] (5, L~(Mes) = [(2 4,6-Me_3C_6H_2)NC(Me)]_2), and a potassium complex, [(~HL~(iPr))_2K_4(THF)_2]_n (3), have been synthesized by alkali metal reduction of the corresponding LZnCl_2 precursors. The Zn_Zn bond in 1 (2.3673(6) _) is slightly shorter than that in the analogous compounds [M(THF)_2]_2[L~iPr)Zn_ZnL~(iPr)] (L~(iPr) = [(2,6-~iPr_2C_6H_3)NC(Me)]_2 M = Na, 2.399(1) _; M = K, 2.393(1) _). 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 C_2N_2 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