Synthesis and crystal structure of two novel polymorphs of (NaCl)[Cu(HSeO3)2]: a further contribution to the family of layered copper hydrogen selenites

Abstract

AbstractCrystals of two new polymorphic forms of the known compound (NaCl)[Cu(HSeO3)2], which we term polymorphsIIandIII, were formed after aca. one-year dwelling of a crystalline precipitate under mother liquor and upon crystallization in the presence of K+, respectively. Both structures belong to the “layered copper hydroselenite” family. The polymorphIIis a structural analog of (KCl)[Cu(HSeO3)2] with a fully ordered Na+site; the main difference concerns the environment of Cu2+which is more regular in (NaCl)[Cu(HSeO3)2]-II. In contrast to some expectations, crystallization from solutions containing KCl. NaCl, CuCl2, and H2SeO3upon evaporation does not result in formation of mixed (Na1−xKxCl)[Cu(HSeO3)2] crystals, but rather in a separate crystallization of (KCl)[Cu(HSeO3)2] and (NaCl)[Cu(HSeO3)2]-IIIwhich exhibits a complex structure with four ordered and one disordered Na+sites. It is possible that longer crystallization times enhance formation of ordered structures.