Mercury-chalcogenide clusters:: Synthesis and structure of [Hg10Te4(SePh)12(PPhnPr2)4], [Hg10Te4(TePh)12(PPhnPr2)4] and [Hg34Te16(SePh)36(PPhnPr2)4]

The reaction of HgCl2 with PPhnPr(2), Te(SinBu(3))(2) and PhESiMe3 (E = Se, Te) in DME at -30 degreesC results in the formation of yellow octahedral crystals of [Hg10Te4(SePh)(12)(PPhnPr(2))(4)] and [Hg10Te4(TePh)(12)(PPhnPr(2))(4)] respectively. The molecular structures of the clusters are similar to those of other [M10Se4-(SePh)(12)(PR3)(4)] (M = Cd, Zn; R = org. group) cluster compounds, but are the first of this type with tellurium as the group 16 metal atom. Dissolution of [Hg10Te4- (SePh)(12)(PPhnPr(2))(4)] in benzene/toluene at 5 degreesC leads to the formation of the larger cluster [Hg34Te16(SePh)(36)(PPhnPr(2))(4)] which displays a new structure type for group 12-16 cluster molecules. The Hg34Te16Se36 cluster core can be considered as an idealized tetrahedral fragment, 15 A in diameter, of the cubic sphalerite lattice with a vacancy in the center. Theoretical investigations on the basis of density functional theory (DFT) reproduce the structural data and the measured electronic spectra for this cluster. Additionally we found that formal occupation of the vacancy by a mercury ion would lead to an ionic cluster [Hg35Te16(SeMe)(36)(PMe3)(4)](2+) which should be stable according to the results of the calculations. This suggests that the formation of the vacancy is probably driven by the absence of an appropriate counterion in the reaction which might stabilize such an ionic cluster molecule. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.