Chromium coordination compounds with bis(3,5-dimethylpyrazol-1-yl) acetic acid or its anion

Two chromium(III) coordination compounds synthesized from a solution of the tridentate (NON) ligand bis(3,5-dimethylpyrazol-1-yl)acetic acid (HL' Hbdrnpza), namely [Cr(L)(2)](H(NO3)2) (1) and [Cr(HL)CI3] (2), are reported. The centrosymmetric central coordination sphere in compound I is fulfilled by two deprotonated ligands L- giving sterically closed coordination shell with pink-orange colored CrO2N4 chromophore. The coordination cation is accompanied by the dinitratohydrogenate(1-) counter anion. Contrary to compound 1, the compound 2 shows only one Hbdmpza ligand, which is protonated HI, though with the same three coordinate N,O,N atoms. Both title compounds 1 and 2 were isolated from the acetonitrile solution with the starting counter-anion remaining in the final product as a new counter anion H(NO3)(2-) in 1, or the coordinated chloride anions in 2 with green colored CrON2Cl3 chromophore. We were able to isolate the single crystals of I, while only polycrystalline material for 2. Nevertheless, the crystal structure of 2 containing two octahedral coordination molecules in the asymmetric unit was determined via the combination of DFF calculations and the powder XRD analysis. Though both compounds reveal a mononuclear octahedral coordination motif, the catalytic accessibility of the compound 2, due to only one tridentate ligand L (HL) per one Cr(III) centre clearly promises more to this aspect. (C) 2014 Elsevier Ltd. All rights reserved.