Syntheses, structures, and magnetic and optical properties of the compounds [Hg3Te2][UCl6] and [Hg4As2][UCl6]

Two new quaternary salts, Hg₃Te₂]UCl₆] and Hg₄As₂]UCl₆], have been synthesized and their structures determined by single-crystal X-ray diffraction analysis. Hg₃Te₂]UCl₆] is the product of a reaction involving UCl₄, HgCl₂, and HgTe at 873 K. The compound crystallizes in space group P2₁/c of the monoclinic system. Hg₄As₂]UCl₆] results from the reaction of U, Hg₂Cl₂, and As at 788 K. It crystallizes in space group Pbca of the orthorhombic system. Hg₃Te₂]UCl₆] has a two-dimensional framework of layers, whereas Hg₄As₂]UCl₆] has a three-dimensional framework of layers interconnected by Hg atoms linearly bonded to As atoms. Both framework structures contain discrete UCl₆]²⁻ anions between the layers. Hg₃Te₂]UCl₆] exhibits temperature-independent paramagnetism. The optical absorption spectra of these compounds display f-f transitions.