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 I 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 A for 1, 3.036 Angstrom for 2 and 3.085 and 3.119 Angstrom for 3. 1: Space group P (1) over bar, Z=1, lattice constants at 20 degreesC: a=7.000(2), b=7.526(2), c=8.239(2)Angstrom: alpha =88.39(2), beta =86.06(2), gamma =86.10(3)degrees, R-1=0.040. 2: Space group P2(1)/c. Z=2, lattice constants at -50 degreesC: a=7.185(1), b=16.338(2),c=7.814(1) Angstrom; beta =94.88(2)degrees; R-1=0.033. 3: Space group P2(1)/n, Z=4, lattice constants at 20 degreesC: a=8.055(3), b=13.101(3), c=13.814(3)Angstrom; beta =91.24(3)degrees; R-1=0.092.