Synthesis and crystal structures of two new lead(II) hexafluoroarsenates(V)

In the system PbF2/AsF5/anhydrous hydrogen fluoride (aHF) two new lead(II) hexafluoroarsenates(V) Pb(HF)(AsF6)2 and PbFAsF6 were isolated. Pb(HF)(AsF6)2 is formed when the molar ratio AsF5:PbF2 is 2 or higher. It crystallizes in the space group Pbcn with a=1058.3(3) pm, b=1520.9(6) pm, c=1079.4(3) pm, V=1.7374(10) nm3 and Z=8. The HF molecule is directly connected to the Pb center, eight fluorine atoms from three different AsF6− ions (Pb–F distances ranging from 248(4) to 276(2) pm) and one further fluorine at 306(3) pm complete the coordination sphere. PbFAsF6 is obtained when equimolar amounts of PbF2 and AsF5 react in aHF. PbFAsF6 crystallizes in the space group P1̄ with: a=466.10(10) pm, b=723.70(10) pm, c=747.40(10) pm, α=105.930(10)°, β=101.49(2)°, γ=90.660(10)°, V=0.23698(7) nm3 and Z=2. The basic unit in the structure of PbF(AsF6) consists of a four-membered ring of two Pb and two F atoms. The Pb atoms in the ring are further connected by two AsF6− units via cis-fluorine bridges, thus forming a [PbF(AsF6)]2 cluster, which interacts by additional Pb–F bonds thus forming a ribbon-like polymer.