New mixed-valence chromium structure type: NH4Cr(CrO4)2
Journal article, 2006

Synthesis and crystal structure of a new structure type of mixed Cr(III)/Cr(VI) chromates is reported. NH4Cr(CrO4)2 was prepared from CrO3 in the presence of (NH4)2Ce(NO3)6. Since this is the first preparation of mixed valence ternary chromium oxides from aqueous solution, a reaction pathway for this synthesis is suggested. The crystal structure of NH4Cr(CrO4)2 has been determined from three-dimensional X-ray data collected at low temperature, 173 K. The structure belongs to the orthorhombic space group Pnma, with a=14.5206(10), b=5.4826(4), c=8.7041(7) Å and Z=4. The title compound consists of corner-sharing chromium(III) octahedra and chromium(VI) tetrahedra forming a three-dimensional network with the composition [Cr(CrO4)2]nn–, containing channels in which zigzag rows of ammonium ions balance the net charge.

mixed valence chromate

Cr(VI)/Ce(III) redox reaction


X-ray diffraction

mixed-valence ternary oxide


Barbara M. Casari

University of Gothenburg

Erica Wingstrand

Royal Institute of Technology (KTH)

Vratislav Langer

Chalmers, Chemical and Biological Engineering, Environmental Inorganic Chemistry

Journal of Solid State Chemistry

0022-4596 (ISSN) 1095-726X (eISSN)

Vol. 179 1 296-301

Subject Categories

Inorganic Chemistry



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