Dirubidium aquapentachlorochromate(III) and dicaesium aquapentachlorochromate(III)

The structures of the two novel title compounds, Rb2[CrCl5(H2O)], (I), and Cs2[CrCl5(H2O)], (II), have been determined by single-crystal X-ray diffraction. Compounds (I) and (II) crystallize with Pnma and Cmcm symmetry, respectively. In (I), the Cr, three Cl and water O atom lie on a mirror plane; in (II), the Cs, Cr, O and one of the Cl atoms are at sites with m2m symmetry. The chromate anions are in a pseudo-cubic environment of eight Rb+ cations in (I) and in a pseudo-octahedral environment of six Cs+ cations in (II). The structural arrangement correlates with the r(anion)/r(cation) radius ratio