Synthesis and Crystal Structure of CuC₄O₄·2 H₂O

The monoclinic compound CuC 4 O 4 ·2 H 2 O (space group P 2 1 /c) was prepared from aqueous acetate buffered solution. The structure was solved from a twinned crystal. Chains consisting of squarate dianions and Cu 2+ , which is coordinated octahedrally in a strongly distorted manner, are the main feature. Only two squarate oxygen atoms contribute considerably to the coordination of Cu 2+ . Neighbouring chains share common oxygen atoms (H 2 O . O squarate ) of the coordination polyhedra. Furthermore the chains are very probably interlinked by strong hydrogen bonds. Thermal decomposition of CuC 4 O 4 ·2 H 2 O leads to CuO.