Preparation And Crystal Structures Of (Hg3 )(PO4 )Cl, (Hg3)(AsO4)Cl And (Hg3)(AsO4)Br - Mercury Compounds With The Triangular Hg3 4+ Cluster

Abstract

The compounds (Hg3)(PO4)Cl, (Hg3)(AsO4)Cl and (Hg3)(AsO4 )Br have been prepared under hydrothermal conditions at 200 °C, starting from stoichiometric mixtures of the corresponding mercury halides and mercury phosphates or arsenates, respectively. The formula (Hg3)(AsO4)Cl is identical with that of the mineral kuznetsovite. All compounds are isotypic and crystallize with four formula units in the space group P21 3 [(Hg3)(PO4)Cl: a = 8.2912(5) Å; (Hg3)(AsO4)Cl: a = 8.3983(6) Å; (Hg3)(AsO4)Br: a = 8.4611(5) Å]. All crystal structures have been refined from single crystal diffractometer data sets under consideration of merohedral twinning according to a diagonal mirror plane as twin element. The structures comprise of equilateral mercury triangles with mean distances d̄(Hg-Hg) = 2.659 Å, which are bonded to halogen and oxygen atoms of nearly perfect PO4 or ASO4 tetrahedra, respectively