Crystal structure of ammonium bis­(pyridine-2,6-di­carboxyl­ato-κ3 O,N,O′)chromate(III) from synchrotron data

The structure of the title compound, (NH4)[Cr(pydc)2] (pydc is pyridine-2,6-di-carboxyl-ate, C7H3NO4), has been determined from synchrotron data. The Cr(III) ion and the N atom of the ammonium cation are located on a crystallographic fourfold rotoinversion axis (-4). The Cr(III) cation is coordinated by four O atoms and the two N atoms of two meridional pydc ligands, displaying a distorted octa-hedral geometry. The Cr-N and Cr-O bond lengths are 1.9727 (15) and 1.9889 (9) Å, respectively. The crystal structure is stabilized by inter-molecular hydrogen bonds involving the N-H groups of the ammonium cation and pyridine C-H groups as donors and the non-coordinating carbonyl O atoms as acceptors.