Crystal structures of Cd(ReO4)2 · 4Urea, Cd(ReO4)2 · 6Urea and Ca(ReO4)2 · 5Urea. Synthesis and characterization of urea adducts from the systems M(ReO4)2-Urea-H2O, M = Ca, Sr, Ba, Pb and Cd

Abstract

The crystal structutes of Cd(ReO4)2 · 4Urea, Cd(ReO4)2 · 6Urea and Ca(ReO4)2 · 5Urea were solved. Cd(ReO4)2 · 4Urea consists of discrete neutral [Cd(ReO4)2L4] (L = Urea) clusters. Ca(ReO4)2 · 5Urea and Cd(ReO4)2 · 6Urea are built up of cationic [Ca(ReO4)L5]+ and [CdL6]2+ clusters, respectively, and ReO4- anions, interlinked by an extensive network of H-bonds. The octahedral coordination of M atoms is most regular in Cd(ReO4)2 · 6Urea and most distorted in Ca(ReO4)2 · 5Urea. With the synthesis and X-ray analysis of these new urea adducts the investigation of the systems M(ReO4)2-Urea-H2O, M = Ca, Sr, Ba, Pb and Cd, was accomplished. This paper represents and a review of the synthesis, X-ray study and IR characterisation of the stable phases from the mentioned systems.