Synthesis and crystal structure of poly[[μ-chlorido-μ-(2,3-dimethylpyrazine)-copper(I)] ethanol hemisolvate], which shows a new isomeric CuCl(2,3-dimethylpyrazine) network

Abstract

Reaction of copper(I)chloride with 2,3-dimethylpyrazine in ethanol leads to the formation of the title compound, poly[[μ-chlorido-μ-(2,3-dimethylpyrazine)-copper(I)] ethanol hemisolvate], {[CuCl(C6H8N2)]·0.5C2H5OH}n or CuCl(2,3-dimethylpyrazine) ethanol hemisolvate. Its asymmetric unit consists of two crystallographically independent copper cations, two chloride anions and two 2,3-dimethylpyrazine ligands as well as one ethanol solvate molecule in general positions. The ethanol molecule is disordered and was refined using a split model. The methyl H atoms of the 2,3-dimethylpyrazine ligands are also disordered and were refined in two orientations rotated by 60° relative to each other. In the crystal structure, each copper cation is tetrahedrally coordinated by two N atoms of two bridging 2,3-dimethylpyrazine ligands and two μ-1,1-bridging chloride anions. Each of the two copper cations are linked by pairs of bridging chloride anions into dinuclear units that are further linked into layers via bridging 2,3-dimethylpyrazine coligands. These layers are stacked in such a way that channels are formed in which the disordered solvent molecules are located. The topology of this network is completely different from that observed in the two polymorphic modifications of CuCl(2,3-dimethylpyrazine) reported in the literature [Jess & Näther (2006). Inorg. Chem. 45, 7446–7454]. Powder X-ray diffraction measurements reveal that the title compound is unstable and transforms immediately into an unknown crystalline phase.

Keywords

• synthesis
• copper(i) coordination polymer
• 2,3-dimethylpyrazine
• crystal structure