Monoclinic Cu₃(SeO₃)₂Cl₂: an oxo­halide with an unusual CuO₄Cl trigonal-bipyramidal coordination

The structure of monoclinic Cu₃(SeO₃)₂Cl₂ is based on layers of CuO₄Cl trigonal bipyramids, CuO₄ square planes and SeO₃E tetra­hedra. The Cu polyhedra are connected by edge- and corner-sharing to form [010] chains and these chains are bridged by the Se atoms to form (001) layers. The compound is isostructural with Cu₃(TeO₃)₂Br₂.