Crystal structure of tris-[4-(di-methyl-amino)-pyridinium] tris-(oxalato-κ(2) O,O')chromate(III) tetra-hydrate.

In the title hybrid salt, (C7H11N2)3[Cr(C2O4)3]·4H2O, the central Cr(III) ion of the complex anion (point group symmetry 2) is coordinated by six O atoms from three chelating oxalate(2-) ligands in a slightly distorted octa-hedral coordination sphere. The Cr-O bond lengths vary from 1.9577 (11) to 1.9804 (11) Å, while the chelate O-Cr-O angles range from 82.11 (6) to 93.41 (5)°. The 4-(di-methyl-amino)-pyridinium cations (one situated in a general position and one on a twofold rotation axis) are protonated at the pyridine N atoms. In the crystal, N-H⋯O and O-H⋯O hydrogen bonds link the cations and anions into a three-dimensional network. π-π inter-actions between the pyridine rings of adjacent cations provide additional stabilization of the crystal packing, with the closest centroid-to-centroid distances being 3.541 (1) and 3.575 (1) Å.

Crystal structure of 4-(di-methyl-amino)-pyridinium cis-di-aqua-bis-(oxalato-κ(2) O,O')ferrate(III) hemihydrate.

The Fe(III) ions in the hybrid title salt, (C7H11N2)[Fe(C2O4)2(H2O)2]·0.5H2O, show a distorted octa-hedral coordination environment, with four O atoms from two chelating oxalate dianions and two O atoms from two cis aqua ligands. The average Fe-O(oxalate) bond length [2.00 (2) Å] is shorter than the average Fe-O(water) bond length [2.027 (19) Å]. The ionic components are connected via inter-molecular N-H⋯O and O-H⋯O hydrogen bonds into a three-dimensional network.

Pyridinium trans-di-aqua-bis-[oxalato(2-)-κ(2) O (1),O (2)]chromate(III) urea monosolvate.

The asymmetric unit of the title solvated mol-ecular salt, (C5H6N)[Cr(C2O4)2(H2O)2]·CO(NH2)2, contains half a formula unit. Each component is completed by crystallographic twofold symmetry: in the cation, one C and the N atom lie on the rotation axis; in the anion, the Cr(III) ion lies on the axis; in the solvent mol-ecule, the C and the O atom lie on the axis. The aqua ligands are in a trans disposition in the resulting CrO6 octa-hedron. In the crystal, the components are linked by O-H⋯O, N-H⋯O and N-H⋯(O,O) hydrogen bonds, generating a three-dimensional network.

catena-Poly[[[(oxamide dioxime-κ2N,N')copper(II)]-µ-L-tartrato-κ4O1,O2:O3,O4] tetrahydrate]: a chiral nanochannel framework hosting solvent water molecules.

The crystal structure of the title compound, {[Cu(C(4)H(4)O(6))(C(2)H(6)N(4)O(2))]·4H(2)O}(n), contains the central Cu(II) cation in a distorted octahedral coordination, symmetrically chelated by the two imine N atoms of a neutral oxamide dioxime (H(2)oxado) ligand [Cu-N = 1.9829 (16) Å] and unsymmetrically bis-chelated by two halves of the L-(+)-tartrate(2-) (tart) ligands, each half being linked to the Cu(II) cation via the deprotonated carboxylate group and protonated hydroxy group [Cu-O = 1.9356 (14) and 2.4674 (13) Å, respectively]. The extended asymmetric unit is defined by twofold axes, one passing through the Cu(II) cation and the centre of the oxamide dioxime (H(2)oxado) ligand and the another two (symmetry related) bisecting the central C-C bonds of the tartrate ions. The structure is chiral, consisting of enantiomeric linear-chain polymers oriented along [001], with virtual monomeric {Cu(tart(0.5))(2)(H(2)oxado)} repeat units and with the chains interleaved face-to-face into `twin pillars'. Nanochannels exist, running parallel to the c axis and bisecting a and b, which host `double strings' of solvent water molecules. Extensive hydrogen bonding (O-H···O and N-H···O) between the chains and solvent water molecules, together with extended π-σ interactions, consolidate the bulk crystal structure.

2-Amino-pyridinium trans-diaqua-bis-(oxalato-κ(2)O,O)chromate(III).

In the title hybrid salt, (C(5)H(7)N(2))[Cr(H(2)O)(2)(C(2)O(4))(2)], the Cr(III) ion is coordinated in a slightly distorted octa-hedral environment by four O atoms from two oxalate ligands in the equatorial plane and by two water O atoms in the axial sites. The 2-amino-pyridinium cation is disordered over two sets of sites in a 0.800 (7):0.200 (7) ratio. In the crystal, N-H⋯O and O-H⋯O hydrogen bonds connect the components into a three-dimensional network. The crystal studied was an inversion twin with components in a ratio 0.75 (2):0.25 (2).

Pyridinium cis-diaqua-bis-(oxalato-κ(2)O,O')chromate(III).

The title compound, (C(5)H(6)N)[Cr(C(2)O(4))(2)(H(2)O)(2)], contains one protonated pyridine mol-ecule and one [Cr(C(2)O(4))(2)(H(2)O)(2)](-) complex anion in the asymmetric unit. The Cr(III) in the complex anion is coordinated in a distorted octa-hedral environment by two O atoms from two cis water mol-ecules and four O atoms from two chelating oxalate dianions. The crystal packing is stabilized by inter-molecular N-H⋯O(oxalate) and O-H⋯O(oxalate) hydrogen bonds and by π-π stacking inter-actions (centroid-centroid distance = 3.602 Å) between pyridine rings, thereby building up a three-dimensional network.

{[Na1(µ-H(2)O)Na2](2)[(C(2)O(4))(2)Cr(µ-OH)(2)Cr(C(2)O(4))(2)]·H(2)O}(n), a novel hydrated form.

The unit cell of the title compound, poly[[µ-aqua-µ-hydroxido-di-µ-oxalato-chromium(III)disodium] monohydrate], {[CrNa(2)(C(2)O(4))(2)(OH)(H(2)O)]·H(2)O}(n), contains four [Na1(µ-H(2)O)Na2][(C(2)O(4))(2)Cr(µ-OH)·H(2)O] formula units, each of which consists of two crystallographically independent Na(+) sites (bridged by one aqua ligand), one half of a centrosymmetric di-µ-hydroxido-bis-[cis-bis-(oxalato)chromate(III)] dimer, [(C(2)O(4))(2)Cr(µ-OH)(2)Cr(C(2)O(4))(2)](4-), and one uncoordin-ated water mol-ecule. The structure is best described as a coordination polymer in which the three-dimensional lattice framework is realized by the inter-connection of the metallic atoms via the O atoms of the aqua, hydroxide and oxalate ligands. One Na atom is hepta-coordinated by one water, one hydroxide and five oxalate O atoms, whilst the other is penta-coordinated by one water and four oxalate O atoms. The coordination around the Cr(3+) sites is pseudo-octa-hedral, involving four aqua and two hydroxide O atoms. Adjacent Na atoms are separated by 3.593 (2) Å, whereas the intra-dimer Cr⋯Cr spacing is 2.978 (1) Å. The crystal structure is consolidated by extended relatively weak O-H⋯O hydrogen bonding with O⋯O distances ranging from 2.808 (4) to 3.276 (5) Å.

4-(Dimethyl-amino)-pyridinium trans-diaqua-bis-[oxalato(2-)-κO,O]chromate(III).

In the title salt, (C(7)H(11)N(2))[Cr(C(2)O(4))(2)(H(2)O)(2)], the asymmetric unit contains one half-cation and one half-anion. The Cr atom, the C and N atoms involved in C- N(exocyclic) bonding and the N and H atoms of N-H groups lie on twofold rotation axis. The Cr(III) atom of the complex anion is six-coordinated in a distorted (4 + 2) octa-hedral geometry with four equatorial O atoms of two nearly coplanar oxalate and two quasi-axial aqua O atoms. In the crystal, the protonated N atoms of the pyridine rings are hydrogen bonded to the carbonyl O atoms of the anions, forming chains along [010]. These chains are connected by lateral O-H⋯O hydrogen bonds, stabilizing the structure.

Tris(oxamide dioxime-κN,N')nickel(II) sulfate penta-hydrate.

The asymmetric unit of the title compound, [Ni(C(2)H(6)N(4)O(2))(3)]SO(4)·5H(2)O, contains two complex cations, two sulfate anions and ten lattice water mol-ecules. In both independent cations, the central Ni(II) ion adopts a distorted octa-hedral coordination involving six imino N atoms of three bidentate oxamide dioxime ligands. The bulk structure is achieved by a three-dimensional network of O-H⋯O and N-H⋯O hydrogen bonds which inter-link the ionic partners and some water mol-ecules in such a manner that the lattice framework thus formed defines channels parallel to [100]. The other water mol-ecules are lodged inside these channels. Two of the ten water mol-ecules in the asymmetric unit are disordered over three sites, in 0.356 (3):0.324 (5):0.320 (5) and 0.247 (3):0.293 (6):0.460 (6) occupancy ratios, and one O atom of a sulfate ion is also disordered over two sites, with occupancies of 0.621 (5) and 0.379 (5).

Monoclinic polymorph of poly[[di-µ-aqua-triaquadi-µ-oxalato-barium(II)-copper(II)] monohydrate].

A monoclinic polymorph of the title compound, {[BaCu(C(2)O(4))(2)(H(2)O)(5)]·H(2)O}(n), is reported. The structure is best described as a coordination polymer where the Cu(II) and Ba(II) centers are coordinated by five and nine O atoms, respectively, in capped quadratic antiprismatic and tetragonal pyramidal geometries. The polymerization arises due to the presence of bridging mono- and bidentate oxalate ligands as well as bridging water mol-ecules. The crystal structure is consolidated by a three-dimensional network of hydrogen bonding.