Synthesis and crystal structure of di-μ-chlorido-bis-[bis(2,6-di-methyl-pyrazine)-copper(I)] and di-μ-bromido-bis[bis(2,6-di-methyl-pyrazine)copper(I)].

Crystals of [Cu2Cl2(C6H8N2)4] (1) and of [Cu2Br2(C6H8N2)4] (2), C6H8N2 = 2,6-di-methyl-pyrazine, were obtained from the reaction of CuCl or CuBr with 2,6-di-methyl-pyrazine in aceto-nitrile under solvothermal conditions. Both compounds are isotypic. The asymmetric unit of each compound consists of one Cu cation, one halide anion and one 2,6-di-methyl-pyrazine ligand in general positions. The copper cations are tetra-hedrally coordinated by two μ-1,1 bridging halide anions and two terminal 2,6-di-methyl-pyrazine ligands. Two copper cations are linked by the two halide anions via common edges into discrete dinuclear complexes that are located on centers of inversion. The discrete complexes are linked by inter-molecular C-H⋯X (X = Cl, Br) hydrogen bonding into chains that propagate along the a-axis direction. Between these chains, additional C-H⋯X inter-actions are observed, which might be stronger for compound 1.