Syntheses and characterization of (diamine-N,N'-dicarboxylato)chromate(III) dinuclear complexes bridged by pyrazole-3,5-dicarboxylate: X-ray structures of Na[Cr-2(edda)(2)(mu-pzdc)]center dot 5H(2)O and Na[Cr-2(trdda)(2)(mu-pzdc)]center dot 3H(2)O

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, H-2 NMR, FAB mass spectra, and X-ray analyses. Crystallographic data for Na[Cr-2(edda)(2)(mu-pzdc)]. 5H(2)O (1) are monoclinic with space group P2(1)/n, a = 11.73(1) Angstrom, b = 19.475(6) Angstrom, c = 13.229(6) Angstrom, beta = 111.99(5)degrees, Z = 4, and a final IZ factor of 0.056 based on 4673 reflections. Na[Cr-2(trdda)(2)(mu-pzdc)]. 3H(2)O (2) crystallizes in the orthorhombic space group Fdd2, with a = 16.576(4) Angstrom, b = 29.235(6) Angstrom, c = 12.544(5) Angstrom, Z = 8, and a final R factor of 0.078 based on 2456 reflections. In both complexes two Cr(III) units were bridged by b 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.