Halogenomercurate: Darstellung und Strukturen von [Cu(en)2][Hg2Cl6], [Cu(en)2][Hg2Br6] und [Cu(en)2][HgBr4]

Halomercurates: Syntheses and Crystal Structures of Cu(en)₂]Hg₂Cl₆], Cu(en)₂]Hg₂Br₆], and Cu(en)₂]HgBr₄] Crystals of Cu(en)₂]Hg₂Cl₆] ( 1 ) have been obtained by layering a solution of Hg(NO₃)₂ and NaCl with a solution of Cu(en)₂]SO₄. An analogous procedure, using NaBr instead of NaCl, gave crystals of Cu(en)₂]HgBr₄] ( 3 ). Crystals of Cu(en)₂]Hg₂Br₆] ( 2 ) were obtained by gel crystallization using the same starting materials as for 3 . The complexes show very low solubility. The dinuclear anions of 1 consist of two nearly planar HgCl₃ units related by a center of symmetry. In 2 infinite anionic chains are present, made up of parallel HgBr₃ units. These units are packed in such a way as to produce a trigonal bipyramidal configuration around the Hg atoms. 3 contains mononuclear deformed tetrahedral HgBr₄]^2– anions. In all three complexes the packing of the ions is such that halogen atoms of halomercurate anions complete a tetragonal bipyramidal coordination at Cu. The resulting Cu–Halogen distances are 2.924 Å for 1 , 3.036 Å for 2 and 3.085 and 3.119 Å for 3 . 1 : Space group P 1, Z = 1, lattice constants at 20 °C: a = 7.000(2), b = 7.526(2), c = 8.239(2) Å; α = 88.39(2), β = 86.06(2), γ = 86.10(3)°; R₁ = 0.040. 2 : Space group P2₁/c, Z = 2, lattice constants at –50 °C: a = 7.185(1), b = 16.338(2), c = 7.814(1) Å; β = 94.88(2)°; R₁ = 0.033. 3 : Space group P2₁/n, Z = 4, lattice constants at 20 °C: a = 8.055(3), b = 13.101(3), c = 13.814(3) Å; β = 91.24(3)°; R₁ = 0.092.