SYNTHESES AND CRYSTAL-STRUCTURES OF THE POLYSELENIDO MERCURATES (PPH4)2[HG(SE4)2] AND [CS(18-CROWN-6)]2[HG2(SE4)3]

(PPh4)2[Hg(Se4)2] has been prepared by the reaction of (PPh4)2[Sn(Se4)3] with Hg(CH3COO)2 in dimethylformamide (DMF) solution. [Cs(18-crown-6)]2[Hg2(Se4)3] has been prepared by the reaction of a lithium polyselenide solution in DMF with Hg(CH3COO)2 in the presence of CsBr and 18-crown-6. Both compounds are obtained as dark red crystals and characterized by X-ray structure determinations. (PPh4)2[Hg(Se4)2]: Space group P2(1)/c, Z = 4, 3021 observed unique reflexions, R = 0.082. Lattice dimensions at 20-degrees-C: a = 1046.0(3), b = 2129.4(2), c = 2213.1(3) pm, beta = 97.62(2)-degrees. The compound consists of PPh4+ ions and anions [Hg(Se4)2]2-, in which the mercury atom is a spirocenter of puckered HgSe4 rings. [Cs(18-crown-6)]2[Hg2(Se4)3]: Space group Ia, Z = 4, 2859 observed unique reflexions, R = 0.074. Lattice dimensions at 20-degrees-C: a = 2018(1), b = 1097.0(2), c = 2317.1(5) pm, beta = 99.40(3)-degrees. The compound forms an ion triple which originates from Cs...Se contacts of 382 to 390 pm with the [Hg2(Se4)3]2- ion. The latter can be described as a [Hg(Se4)2]2- ion, which has contacts with a HgSe4 fragment.