New aquapentotchlorochromate(III) compounds:: K2[CrCl5(H2O)] and (NH4)2[CrCl5(H2O)]

Synthesis and crystal structures of two new compounds, K-2[CrCl5(H2O)] (I) and (NH4)(2)[CrCl5(H2O)] (II) are reported. Both compounds were prepared from chromium(VI) salts by two different methods and reaction pathways of these syntheses are suggested. The crystal structures of these two aquapentachlorochromates(III) have been determined from three dimensional X-ray data collected at low temperature, 173 K. The two structures are isomorphous and their unit cell dimensions are quite similar. They are orthorhombic, space groups Pnma, with Z = 4. Both structures are composed of [CrCl5(H2O)](2-) units held together by the counterion framework. The coordination around the chromium ion deviates from a regular octahedron due to the shorter equatorial chromium-oxygen bond.