Se4CuX, Te4CuX and Cu2Se7X2 (X = GaCl4) — Coordination compounds of neutral infinite chalcogen chains

• Synthetic work performed in gallium trichloride based melts
• Novel helical chalcogen chains are presented.
• The chains resemble the chains in elemental Se and Te, but the conformations are different.
• Copper(I) tetrachlorido gallate units are spacers between the chains.
• The presence of monovalent Cu and thus the neutrality of the chains proven by EPR spectroscopy

The reactions of selenium and tellurium in molten GaCl3 with SbCl3 and copper(II) or copper(I) chloride yielded CuSe4[GaCl4] (1), CuTe4[GaCl4] (2), and Cu2Se7[GaCl4]2 (3). EPR measurements show no resonances, implying the presence of monovalent Cu ions. The structures consist of discrete infinite neutral chalcogen chains of helical shape. Cu(I) ions are coordinated to the Se and Te chains via three chalcogen atoms for the isotypic 1 and 2, and via two Se atoms for 3. The coordination tetrahedron for Cu is completed by coordination of Cl atoms of neighboring [GaCl4]− anions.