Naslov
Unique cadmium(II) dipicolinate coordination tetramers with different Cd(II) coordination environments and number of halide ions (Cl, Br)

Autori
Kukovec, Boris-Marko ; Oliver, Clive L.

Izvornik
Polyhedron (0277-5387) 34 (2012), 1; 46-55

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
Cadmium; Coordination tetramers; Carboxylate ligands; Crystal engineering; Solid-state structures

Sažetak
Cadmium(II) dipicolinate (dipic) coordination tetramers, namely [Cd2Cl(dipic)(dipicH)(H2O)4]2.2H2O (1), [Cd2Br(dipic)(dipicH)(H2O)4]2.2H2O (2), [Cd2Cl2(dipicH)2(H2O)3]2.2H2O (3), [Cd2Br2(dipicH)2(H2O)3]2.2H2O (4) were prepared. The molecular and crystal structures of 1-4 were determined by single crystal X-ray structural analysis. Tetramers 3 and 4 were also characterised by powder X-ray diffraction and thermal methods (TG, DSC and hot-stage microscopy). Tetramers 1-4 were prepared at 60 ˚C under autogenous pressure by reaction of cadmium(II) salt (chloride or bromide) and dipicolinic acid in aqueous solution. The concentration of both reactants and the time of heating crucially effect the preparation of a particular tetramer. The tetramers 3 and 4 can be reproducibly prepared and isolated in high yield as pure compounds, whilst 1 and 2 could not be obtained in a pure form and always as the minor component in the mixture. Tetramers 1 and 2 are isostructural, containing two crystallographically independent 7-coordinated Cd(II) ions bridged by two dipicolinate ligands into a dinuclear unit. Two dinuclear units are centrosymmetrically connected via bridging water molecules into a tetrameric structure. The two 7-coordinated Cd(II) ions have different coordination environments, one having a halide ion substituted with a water molecule. Tetramers 3 and 4 are also isostructural and very similar to 1 and 2, containing 7-coordinated Cd(II) ions coordinated in the same way (including halide ion) as in 1 and 2. The difference in coordination environment of Cd(II) ions for 1 and 2, when compared to 3 and 4, is also reflected in different hydrogen bond motifs found in the crystal structures, i.e. R44(8) for 1 and 2 or R33(10) for 3 and 4.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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