Syntheses, crystal structures and magnetic properties of four CuII-HgII mixed-metal halide oligomers

Four heteronuclear Cu-II-Hg-II halides containing 2,2-bipyridine (bipy) ligands have been synthesized and structurally characterised by single-crystal X-ray diffraction studies. The dinuclear complex [Cu(bipy)(2)HgCl2Br2] (1) contains a five-coordinate copper(II) ion and a four-coordinate Hg-II ion, in which the two different types of metal ions are bridged by a pair of chloride anions. [Cu-2(bipy)(4)HgBr4][Hg2Br6] (2) contains a trinuclear [Cu-2(bipy)(4)HgBr4](2+) cation in which the two copper(II) ions are bridged by an [HgBr4](2+) tetrahedron via two Cu-Br bonds, and an edge-sharing tetrahedral [Hg2Br6](2-) anion. The structure of [Cu-2(bipy)(4)Hg2Br6][Hg4Br10] (3) features a 1-D chain along the diagonal of the a and c axes constructed from tetranuclear [Cu-2(bipy)(4)Hg2Br6](2+) cations interconnected by [Hg4Br10](2-) tetramers via elongated Hg-Br contacts (3.185 Angstrom). Within the tetranuclear cationic unit, two [Cu(bipy)(2)](2+) units are bridged by an edge-sharing dimeric tetrahedral [Hg2Br6](2-) anion. In the trinuclear complex [Cu(bipy)(2)Hg2Cl6] (4), each [Hg2Cl6](2-) dimer bridges with a [Cu(bipy)(2)](2+) ion to form a trinuclear [Cu(bipy)(2)Hg2Cl6] unit, and each pair of such units is bridged by a pair of elongated Hg-Cl bonds [3.043(5) Angstrom] to form a dimeric unit. The magnetic properties of 1, 2, and 4 have also been investigated. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.