A new heteroleptic oxalate-based compound: poly[[2-(aminomethyl)pyridine]di-μ6-oxalato-chromium(III)potassium(I)].

The title compound, [KCr(C2O2)2(C6H8N2)]n, was obtained from aqueous solution and analyzed with single-crystal X-ray diffraction at 100 K. It crystallizes in the monoclinic space group C2/c and displays a three-dimensional polymeric architecture built up by bimetallic oxalate-bridged Cr(III)-K helical chains linked through centrosymmetric K2O2 units to yield a sheet-like alternating P/M arrangement which looks like that of the previously described two-dimensional [NaCr(ox)2(pyim)(H2O)]·2H2O [pyim is 2-(pyridin-2-yl)imidazole; Lei et al. (2006). Inorg. Chem. Commun. 9, 486-488]. The Cr(III) ions in each helix have the same chirality. The infinite neutral sheets are eclipsed with respect to each other and are held together by a hydrogen-bonding network involving 2-(aminomethyl)pyridine H atoms and oxalate O atoms. Each sheet gives rise to channels of Cr4K4 octanuclear rings and each resultant hole is occupied by a pair of 2-(aminomethyl)pyridine ligands with partial overlap. The shortest Cr...Cr distance [5.593 (4) Å] is shorter than usually observed in the K-M(III)-oxalate family.