Synthesis, characterization and crystal structure of catena-bis(1,10-phenanthroline)-μ-chloranilatocadmium(II): a zig-zag polymer based on eight-coordinated square antiprismatic units

A novel type of coordination mode of chloranilic acid leading to the formation of polymeric coordination ribbon in the series of mixed-ligand copper(II) complexes with 1,10-phenanthroline

A series of four novel mixed-ligand complexes of copper(II) with 3,6-dichloro-2,6-dihydroxy-1,4-benzoquinone (chloranilic acid) and 1,10-phenanthroline was prepared and characterised by X-ray structure analysis and IR spectroscopy. Three complexes exhibit square-pyramidal coordination, whereas one exhibits octahedral coordination. The ligand 1,10-phenanthroline acts in a bidentate chelating mode with N,N-metal binding. The chloranilate dianion coordinates to the Cu(II) atom in a terminal bidentate ortho-quinone-like mode, forming a mononuclear complex species. However, in one structure a novel type of coordination mode of chloranilate is observed. In addition to the bidentate mode, a monodentate bridging mode through a carboxy oxygen of a symmetry-related dianion leads to the formation of polymeric coordination ribbon. The crystal packing of penta-coordinated species, in addition to hydrogen bonding, involves less common stacking interactions of chelate rings with the π-systems of the ligands.

Cadmium-113 NMR studies on homoleptic complexes containing thioether ligands: the crystal structures of [Cd([12]aneS4)2](ClO4)2, [Cd([18]aneS4N2)](PF6)2 and [Cd([9]aneS3)2](PF6)2

We report the measurement of 113Cd NMR chemical shift data for homoleptic thioether and related aza and mixed aza/thiacrown complexes. In a series of Cd(II) complexes containing trithioether to hexathioether ligands, we observe solution 113Cd NMR chemical shifts in the range of 225 to 731 ppm. Upfield chemical shifts in these NMR spectra are seen whenever: (a) the number of thioether sulfur donors in the complex is decreased, (b) a thioether sulfur donor is replaced by a secondary nitrogen donor, or (c) the size of the macrocycle ring increases without a change in the nature or number of the donor atoms. Changes in the identity of non-coordinating anions such as perchlorate or hexafluorophosphate have little effect upon the 113Cd NMR chemical shift in solution. We report the X-ray structure of the complex [Cd([12]aneS4)2](ClO4)2 ([12]aneS4 = 1,4,7,10-tetrathiacyclododecane) (1) which shows the first example of octakis(thioether) coordination of a metal ion, forming an unusual eight-coordinate square antiprismatic structure. We report the X-ray structure of the complex [Cd([9]aneS3)2](PF6)2 ([9]aneS3 = 1,4,7-trithiacyclononane) (3a) which shows hexakis(thioether) coordination to form a distorted octahedral structure. We have also prepared and characterized the Cd(II) complex of a mixed azathiacrown, [Cd([18]aneS4N2)](PF6)2 ([18]aneS4N2 = 1,4,10,13-tetrathia-7,16-diazacyclooctadecane) (6). Its X-ray structure shows a distorted octahedral S4N2 environment around the Cd(II) with the ligand coordinated in the rac fashion. We observe a solvent- and temperature-dependent 14N-1H coupling in the 1H NMR spectrum of the complex which is not present in analogous complexes with this ligand.