Glycine coupled to a bis(imidazole): a tetradentate ligand rendering dinuclear copper(II) compounds through ligand sharing
作者:Colm J. Campbell、Willem L. Driessen、Jan Reedijk、Wilberth Smeets、Anthony L. Spek
DOI:10.1039/a802831a
日期:——
The tetradentate ligand (carboxymethylamino)bis(imidazole-2-yl)methane (Hglyim), obtained through the reaction of glycine with bis(imidazol-2-yl)nitromethane, rendered several dinuclear copper(II) compounds, viz. [Cu2(glyim)2Cl2]·6H2O 1, [Cu2(glyim)2Br2]·5H2O 2, [Cu2(glyim)2Cl(H2O)][CF3SO3]·2H2O 3 and [Cu2(glyim)2Cl(H2O)][ClO4]·2H2O 4. The single crystal structure of 1 was determined. It consists of [Cu2(glyim)2Cl2] units and several, mostly disordered, water molecules. The ligands and the anions are grouped in dimers of formula [Cu2(glyim–)2(Cl–)2] in which the two copper(II) ions are entangled by two ligands. Each copper is in a square pyramidal N3OCl environment with the chloride ion occupying the apical position. Two of the co-ordinating nitrogens are from the imidazole groups of one ligand, while an amine nitrogen and a carboxyl oxygen are donated by the other ligand. This 2+2 ligand-sharing arrangement imposes a rather short distance on the two copper(II) ions, i.e. 3.249(2), 3.357(2) and 3.373(2) Å. A well resolved EPR spectrum of 10–3M 3 in MeOH was obtained at 77 K with geff values for Hz1, Hxy1, Hz2 and Hxy2 at 2.69, 2.26, 1.89 and 1.86 respectively, an A|| value of 87 G and a half-field signal at g = 4.24, indicating the preservation of the dinuclearity in solution (D = 0.047 cm–1). At concentrations of 10–4M and lower the dinuclear signals break down and the complex decomposes into monomeric species (g|| = 2.27 and g⊥ = 2.10).
通过甘氨酸与双(咪唑-2-基)硝基甲烷反应获得四齿配体(羧甲基氨基)双(咪唑-2-基)甲烷(Hglyim),得到几种双核铜(II)化合物,即。 [Cu2(glyim)2Cl2]·6H2O 1、[Cu2(glyim)2Br2]·5H2O 2、[Cu2(glyim)2Cl(H2O)][CF3SO3]·2H2O 3 和 [Cu2(glyim)2Cl(H2O)][ ClO4]·2H2O 4.测定了1的单晶结构。它由 [Cu2(glyim)2Cl2] 单元和几个大多无序的水分子组成。配体和阴离子被分组为式[Cu2(glyim–)2(Cl–)2]的二聚体,其中两个铜(II)离子被两个配体缠结。每个铜都处于方锥体 N3OCl 环境中,氯离子占据顶端位置。两个配位氮来自一个配体的咪唑基团,而胺氮和羧基氧则由另一个配体提供。这种 2+2 配体共享排列在两个铜 (II) 离子上施加了相当短的距离,即 3.249(2)、3.357(2) 和 3.373(2) Å。在 77 K 下获得了 MeOH 中 10-3M 3 的高分辨率 EPR 谱图,Hz1、Hxy1、Hz2 和 Hxy2 的 geff 值分别为 2.69、2.26、1.89 和 1.86,A|| 87 G 的值和 g = 4.24 处的半场信号,表明溶液中双核的保留 (D = 0.047 cm–1)。在 10–4M 及更低的浓度下,双核信号分解,复合物分解为单体(g|| = 2.27 和 g⊥ = 2.10)。