Syntheses and Characterization of (Diamine-N,N‘-dicarboxylato)chromate(III) Dinuclear Complexes Bridged by Pyrazole-3,5-dicarboxylate: X-ray Structures of Na[Cr2(edda)2(μ-pzdc)]·5H2O and Na[Cr2(trdda)2(μ-pzdc)]·3H2O

New pyrazole-3,5-dicarboxylato (pzdc) chromate(III) complexes containing linear tetradentate edda (ethylenediamine- N, N‘ -diacetate), trdda (trimethylenediamine- N, N‘ -diacetate), or eddp (ethylenediamine- N, N‘ -dipropionate) were synthesized and characterized by elemental analyses, column chromatography, 2 H NMR, FAB mass spectra, and X-ray analyses. Crystallographic data for Na[Cr 2 (edda) 2 (μ-pzdc)]·5H 2 O ( 1 ) are monoclinic with space group P 2 1 / n, a = 11.73(1) Å, b = 19.475(6) Å, c = 13.229(6) Å, β = 111.99(5)°, Z = 4, and a final R factor of 0.056 based on 4673 reflections. Na[Cr 2 (trdda) 2 (μ-pzdc)]·3H 2 O ( 2 ) crystallizes in the orthorhombic space group Fdd 2, with a = 16.576(4) Å, b = 29.235(6) Å, c = 12.544(5) Å, Z = 8, and a final R factor of 0.078 based on 2456 reflections. In both complexes two Cr(III) units were bridged by a pzdc. The complex 1 and 2 has a (sym- cis )−(unsym- cis ) edda and (unsym- cis )−(unsym- cis ) trdda geometrical configuration, respectively. Unlike the edda and trdda ligands, the eddp ligand formed mononuclear pzdc complexes, which may correspond to two geometrical isomers of unsym- cis - mer - and fac -[Cr(eddp)(pzdc)] 2- ( 3 and 4 ). The differences in the formations of the pzdc Cr(III) complexes with the edda-type ligands were demonstrated to arise from the chelate ring sizes and/or the intramolecular interaction such as hydrogen bond and van der Waals contact between two Cr(III)−edda type units. The hydrogen bond between the edda moieties following stereognostic coordination brings about the novel inert unsym- cis configuration in complex 1 .