Poly[di-µ-aqua-di-aqua-bis-(µ7-oxalato-κ(9) O (1):O (1):O (1),O (2):O (2):O (2'):O (2'),O (1'):O (1'))calciumdicaesium].

In the title compound, [CaCs2(C2O4)2(H2O)4] n , the Ca(2+) ion, lying on a twofold rotation axis, is coordinated by four O atoms from two oxalate ligands and two bridging water mol-ecules in an octa-hedral geometry. The Cs(+) ion is coordinated by seven O atoms from six oxalate ligands, one bridging water and one terminal water mol-ecule. The oxalate ligand displays a scarce high denticity. The structure contains parallel chain units runnig along [10-1], formed by two edge-sharing Cs polyhedra connected by CsO9 polyhedra connected by a face-sharing CaO6 octahedron. These chains are further linked by the oxalate ligands to build up a three-dimensional framework. O-H⋯O hydrogen bonds involving the water mol-ecules and the carboxyl-ate O atoms enhance the extended structure.

Intra- and supra-molecular inter-actions in cis,mer-diaqua-tris-(1H-imidazole-κN(3))(terephthalato-κO)cobalt(II) monohydrate.

In the title compound, [Co(C(8)H(4)O(4))(C(3)H(4)N(2))(3)(H(2)O)(2)]·H(2)O, the cisoid angles are in the range 85.59 (5)-93.56 (5)°, while two equal transoid angles deviate significantly from the ideal linear angle, the third being almost linear. One carboxyl-ate group is almost coplanar [1.23 (13)°] with the plane of its parent aromatic ring, although it has one O-atom donor involved in one coordination and one hydrogen bond as acceptor. The other carboxyl-ate group does not coordinate and is rotated out of this plane with a torsional twist of 17.27 (20)°. The coordination neutral entity, based on aqua ligands and two cyclic co-ligands seems, at first sight, monomeric. Strongly tight, via one intra-molecular hydrogen bond between aqua and carboxyl-ate O atoms, it brings out a quasi-planar six-membered ring around the Co(II) atom, turning the CoN(3)O(3) coordination octa-hedron into a new building block. The rigidity of this feature associated with several hydrogen-bonded arrays yields an extended structure. In the resulting supra-molecular packing, a binuclear hydrated Co(II) assembly, built up from triple strands driven by different heterosynthons, embodies the synergy of coordination, covalent and hydrogen bonds.

Poly[diaquadi-µ6-oxalato-µ5-oxalato-chromium(III)rubidium(I)]: a new supramolecular isomer.

The title compound, [CrRb(C(2)O(4))(2)(H(2)O)(2)](n), obtained under hydrothermal conditions and investigated structurally at 100 K, is a three-dimensional supramolecular isomer of the layered structure compound studied at room temperature. This novel polymer is built up from crosslinked heterobimetallic units. The linkage of alternating edge- and vertex-shared RbO(7)(H(2)O)(2) and CrO(4)(H(2)O)(2) polyhedra running along three different directions gives a dense packing. The two independent ligands display two η(4)-chelation modes and two conventional carboxylate bridges. However, the pentadentate ligand connects the Cr(III) and Rb(I) ions through one O-atom bridge, while the hexadentate ligand exhibits an additional η(3)-chelation and two O-atom bridges. Each coordinated water molecule forms an O-atom bridge between the two metals. Moreover, in the absence of protonated ligands, these water molecules act as donors through their four H atoms in strong-to-weak hydrogen bonds. This results in zigzag chains of alternating oxalate and aqua ligands parallel to the twofold screw axis. The six double oxalates known to date containing an alkali and Cr(III) all present layered two-dimensional structures. In the series, this supramolecular isomer is the first three-dimensional framework.

catena-Poly[[aquabarium(II)]-mu-aqua-bis(mu-2'-carboxybiphenyl-2-carboxylato)].

In the title compound, [Ba{HOOC(C(6)H(4))(2)CO(2)}(2)(H(2)O)(2)] or [Ba(C(14)H(9)O(4))(2)(H(2)O)(2)], the Ba atoms are coordinated by nine O atoms, six from two 2'-carboxybiphenyl-2-carboxylate (Hbpdc(-)) ligands and three from three coordinated water molecules, resulting in the formation of face-sharing distorted monocapped square antiprisms. The Hbpdc(-) ligands bridge the Ba atoms to form a one-dimensional helical polymer, with a Ba...Ba distance across the chain of 4.1386 (17) A. Adjacent chains are parallel to each other. The two independent ligands are tetradentate and have the same coordination mode, exhibiting mu-oxo bridges and eta(8)-chelation. The crystal structure is further stabilized by hydrogen bonds within each chain.