New mixed-valence chromium structure type: NH4Cr(CrO4)2
Artikel i vetenskaplig tidskrift, 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

Göteborgs universitet

Erica Wingstrand

Kungliga Tekniska Högskolan (KTH)

Vratislav Langer

Chalmers, Kemi- och bioteknik, Oorganisk miljökemi

Journal of Solid State Chemistry

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

Vol. 179 296-301


Oorganisk kemi