Showing papers on "Coordination polymer published in 1992"

Into The Third Dimension of Coordination Chemistry: Towards Starburst Arrays

Abstract: The coordination properties of the tridentate ligand 2,2′:6′,2″-terpyridine make it an ideal structural unit to incorporate into monomers to be used for the assembly of coordination polymers. The electronic properties of metal complexes may be subtly controlled by the incorporation of electron withdrawing or electron releasing substituents upon the 2,2′:6′,2″-terpyridine. The synthesis of a range of such ligands is described, and a detailed study of the electronic and solution properties of their homoleptic and heteroleptic ruthenium(II) complexes is reported. Linear coordination oligomers and polymers are readily prepared by the use of bis(2,2′:6′,2″-terpyridine) ligands as linkers, and the synthesis of materials derived from two such linkers is reported. The electronic properties of these compounds may be controlled by the introduction of suitably substituted terminator ligands. The synthesis of a novel tris(2,2′:6′,2″-terpyridine) ligand is reported which forms an extended three-dimensional coordination polymer. The preparation and characterisation of a single triruthenium unit from such a polymer is reported.

π-Coordination of ortho-benzoquinone: synthesis and structure of [{Ru2(η4-µ2-o-C6H4O2)(CO)4(AsPh3)}2] and [Ru2(η4-µ2-o-C6H4O2)(CO)4(µ2-I)I]

Abstract: The coordination polymer prepared by treating [Ru3(CO)12] with catechol can be cleaved with either a Lewis base or iodine to give products containing η4-ortho-benzoquinone ligands, two of which, [{Ru2(η4-µ2-o-C6H4O2)(CO)4(AsPh3)}2] and [Ru2(η4-µ2-o-C6H4O2)(CO)4(µ2-I)I] are structurally characterized by X-ray diffraction.

Metal Binding by Amino Acids: Preparation and Crystal Structures of Lithium, Sodium, and Potassium Hydrogen Bis‐L‐pyroglutamate

Abstract: Lithium, sodium and potassium hydrogen bis-L-pyroglutamate [Li(L-pGlu)(L-pGluH)], [Na(L-pGlu)(L-pGluH)] and [K(L-pGlu)(L-pGluH)], respectively, have been prepared by reaction of aqueous solutions of the metal hydroxides with L-pyroglutamic acid in the molar ratio 1:2, or in methanol. Crystalline samples of the salts could be obtained by slow evaporation of solutions of the salts in methanol. In the solid state, Li(L-pGlu)(L-pGluH) adopts a chain structure with the lithium atoms arranged in double strands. Adjacent metal centers are bridged by the carboxylate groups of the L-pGlu− ligands. The L-pGluH ligands are attached to the metal centers through the amide oxygen atoms. Na(L-pGlu)(L-pGluH) forms a three-dimensional coordination polymer with two half-occupied sodium positions, one L-pGlu− and one L-pGluH ligand in the asymmetric unit. The carboxyl and carboxylate groups of the L-pGluH and the L-pGlu− ligands are bridging the sodium centers, giving rise to eight-membered rings, which consist of two sodium atoms, a carboxyl and a carboxylate group. The hydrogen atoms of the carboxyl group of the L-pGluH ligands are involved in strong hydrogen bonds between a carboxyl and an adjacent carboxylate oxygen atom. K(L-pGlu)(L-pGluH) adopts a layer structure with strands of potassium atoms. The metal centers are connected through bridging carboxyl and carboxylate groups of the L-pGluH and L-pGlu− ligands, respectively. The structure features eight-membered ring units comparable to those observed for Na(L-pGlu)(L-pGluH), again with the hydrogen atom of the carboxyl group engaged in a strong transannular hydrogen bond. The amide oxygen atoms of the L-pGlu− and the L-pGluH ligands are coordinated to the metal centers of adjacent coordination chains. The results of 1H- and 13CNMR investigations of aqueous solutions of the compounds indicate extensive electrolytic dissociation in dilute solutions.