Dipotassium tetrachromate(VI), K₂Cr₄O₁₃

The structure of dipotassium tetrachromium(VI) tridecaoxide, K₂Cr₄O₁₃, has been determined from single-crystal X-ray data collected at 173(2)K on a racemically twinned crystal with monoclinic Pc space-group symmetry. The structure is composed of discrete [Cr₄O₁₃]^2- zigzag chains held together by the charge-balancing potassium ions. The conformations adopted by the tetrachromate anion in alkali metal salts and Cr₈O₂₁ are different and can be divided into three categories