Anhydrous CuC4O4, a Channel Structure solved from X-ray Powder Diffraction Data

Abstract

The crystal structure of the new anhydrous metal squarate CuC4O4 was solved from laboratory X–ray powder diffraction data. It crystallizes in the monoclinic space group I2/a (no. 15) with the lattice parameters a = 5.6747(1), b = 8.9394(4), c = 9.4987(4) A und β = 94.372(2)° at ambient conditions (Z = 4, RF2 = 8.24 %). The crystal structure can be reduced to a defect variant of the AlB2 type of structure ([C4O4][Cu □] ⇔ [Al][B2]) and shows channels parallel to the a axis with a free diameter of about 2.3A. The squarate dianion, [C4O4]2−, is acting as a μ6–ligand, in this case.