Disproportionation of Ag(II) to Ag(I) and Ag(III) in fluoride systems and syntheses and structures of (AgF+)(2)AgF4-MF6- salts (M = As, Sb, Pt, Au, Ru)

摘要

Interaction of Ag+ salts in anhydrous liquid hydrogen fluoride, aHF, with AgF4- salts gives amorphous red-brown diamagnetic (AgAgTF4)-Ag-I-F-III, which transforms exothermally to brown, paramagnetic, microcrystalline (AgF2)-F-II below 0 degrees C. (AgAuF4)-Au-I-F-III prepared from Ag+ and AuF4- in aHF has a tetragonal unit cell and a KBrF4 type lattice, with a 5.788(1) Angstrom, c 10.806(2) Angstrom, and Z = 4. Blue-green (AgFAsF6)-F-II disproportionates in aHF (in the absence of F- acceptors) to colorless (AgAsF6)-As-I and a black pseudotrifluoride, ((AgFI)-F-II)(2)(AgF4-AsF6-)-F-III. The latter and other (AgF)(2)AgF4MF6 salts are also generated by oxidation of AgF2 or AgF+ salts in aHF with F-2 or in solutions of O2SMF6- salts (M = As, Sb, Pt, Au, Ru). Single crystals of (AgF)(2)AgF4AsF6 were grown from an AgFAsF6/AsF5 solution in aHF standing over AgF2 or AgFBF4, with F-2 as the oxidant. They are monoclinic, P2/c, at 20 degrees C, with a = 5.6045(6) Angstrom, b = 5.2567(6) Angstrom, c = 7.8061(8) Angstrom, beta = 96.594(9)degrees, and Z = 1. The structure consists of (AgF)(n)(n+) chains (F-Ag-F = 180 degrees, Ag-F-Ag = 153.9(11)degrees, Ag-F = 2.003(4) Angstrom), 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)(2)AgF4AsF6 [like other (AgF)(n)(n+) salts] is a temperature-independent paramagnet except for a Curie "tail" below 50 K. [References: 41]