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

Abstract

A series of mononuclear and dinuclear zinc compounds, [Na(Et₂O)]₂[(^HL^iPr)Zn–Zn(^HL^iPr)]·Et₂O (1), [Zn₂(^HL^iPr)₃K₂(Et₂O)₂]_n (2, ^HL^iPr = [(2,6-ⁱPr₂C₆H₃)NCH]₂), [Zn(^HL^Mes)₂] (4, ^HL^Mes = [(2,4,6-Me₃C₆H₂)NCH]₂), and [ZnL^Mes₂Na₂(THF)₂] (5, L^Mes = [(2,4,6-Me₃C₆H₂)NC(Me)]₂), and a potassium complex, [(^HL^iPr)₂K₄(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) Å) is slightly shorter than that in the analogous compounds [M(THF)₂]₂[L^iPrZn–ZnL^iPr] (L^iPr = [(2,6-ⁱPr₂C₆H₃)NC(Me)]₂, M = Na, 2.399(1) Å; M = K, 2.393(1) Å). 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.