Synthesis, crystal structure and thermal properties of di-μ-iodido-bis-[bis-(2-chloro-pyrazine-κN)copper(I)].

Reaction of copper(I) iodide in pure 2-chloro-pyrazine leads to the formation of a few crystals of the title compound, [Cu2I2(C4H3ClN2)4] or (CuI)2(2-chloro-pyrazine)4, which was characterized by single-crystal X-ray diffraction. In its crystal structure, the CuI cations are each tetra-hedrally coordinated by two iodide anions and two 2-chloro-pyrazine ligands and are linked into binuclear complexes consisting of (CuI)2 rings located on centers of inversion. PXRD investigations of a few crystals obtained from the suspension indicate that the title compound is contaminated with a small amount of the 2-chloro-pyrazine-deficient compound CuI(2-chloro-pyrazine) already reported in the literature. PXRD investigations prove that the title compound immediately decomposes at room temperature into CuI(2-chloro-pyrazine) and this might be the reason why no pure samples can be obtained. TDA-TG-MS investigations shows two mass losses, the first of which corresponds to the formation of CuI(2-chloro-pyrazine), whereas in the second mass loss CuI is formed.