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

The compounds (Hg 3 )(PO 4 )Cl, (Hg 3 )(AsO 4 )Cl and (Hg 3 )(AsO 4 )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 (Hg 3 )(AsO 4 )Cl is identical with that of the mineral kuznetsovite. All compounds are isotypic and crystallize with four formula units in the space group P2 1 3 [(Hg 3 )(PO 4 )Cl: a = 8.2912(5) Å; (Hg 3 )(AsO 4 )Cl: a = 8.3983(6) Å; (Hg 3 )(AsO 4 )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 PO 4 or ASO 4 tetrahedra, respectively