Disproportionation of Ag(II) to Ag(I) and Ag(III) in fluoride systems and syntheses and structures of (AgF⁺)₂AgF₄^-MFe₆ ^- salts (M = As, Sb, Pt, Au, Ru)

Interaction of Ag⁺ salts in anhydrous liquid hydrogen fluoride, aHF, with AgF₄^- salts gives amorphous red-brown diamagnetic Ag^IAg^IIIF₄, which transforms exothermally to brown, paramagnetic, microcrystalline Ag^IIF₂ below 0°C. Ag^IAu^IIIF₄ prepared from Ag⁺ and AuF₄^- in aHF has a tetragonal unit cell and a KBrF₄ type lattice, with a = 5.788(1) Å, c = 10.806(2) Å, and Z = 4. Blue-green Ag^IIFAsF₆ disproportionates in aHF (in the absence of F^- acceptors) to colorless Ag^IAsF₆ and a black pseudotrifluoride, (Ag^IIF⁺)₂Ag^IIIF₄ ^-AsF₆^-. The latter and other (AgF)₂AgF₄MF₆ salts are also generated by oxidation of AgF₂ or AgF⁺ salts in aHF with F₂ or in solutions of O₂⁺MF₆^- salts (M = As, Sb, Pt, Au, Ru). Single crystals of (AgF)₂AgF₄AsF₆ were grown from an AgFAsF₆/AsF₅ solution in aHF standing over AgF₂ or AgFBF₄, with F₂ as the oxidant. They are monoclinic, P2/c, at 20°C, with a = 5.6045(6) Å, b = 5.2567(6) Å, c = 7.8061(8) Å, β = 96.594(9)°, and Z = 1. The structure consists of (AgF)_nⁿ⁺ chains (F-Ag-F = 180°, Ag-F-Ag = 153.9(11)°, Ag-F = 2.003(4) Å), parallel to c, that enclose stacks of alternating AgF₄^- and AsF₆^-, each anion making bridging contact with four Ag(II) cations of the four surrounding chains "caging" them. There is no registry between the ordered array in one "cage" and that in any neighboring "cage". The F-ligand anion bridges between the anions and, with the Ag(II) of the chains, generates a trifluoride-like structure. (AgF)₂AgF₄AsF₆ [like other (AgF)_nⁿ⁺ salts] is a temperature-independent paramagnet except for a Curie "tail" below 50 K.