Concerning the nature of XePtF6

With the aim of gauging their potential as conducting or superconducting materials, we examine the crystal structures and magnetic properties of the roughly one hundred binary, ternary, and quaternary Ag(II) and Ag(III) fluorides in the solid state reported up to date. The Ag(II) cation appears in these species usually in a distorted octahedral environment, either in an [AgF](+) infinite chain or as [AgF(2)] sheets. Sometimes one finds discrete square-planar [AgF(4)](2-) ions. The Ag(III) cation occurs usually in the form of isolated square-planar [AgF(4)](-) ions. Systems containing Ag(III) (d(8)) centers are typically diamagnetic. On the other hand, the rich spectrum of Ag(II) (d(9)) environments in binary and ternary fluorides leads to most diverse magnetic properties, ranging from paramagnetism, through temperature-independent paramagnetism (characteristic for half-filled band and metallic behavior) and antiferromagnetism, to weak ferromagnetism. Ag(II) and Ag(III) have the same d-electron count as Cu(II) (d(9)) and Cu(III) (d(8)), respectively. F(-) and O(2-) ions are isoelectronic, closed-shell (s(2)p(6)) species; both are weak-field ligands. Led by these similarities, and by some experimental evidence, we examine analogies between the superconducting cuprates (Cu(II)/Cu(III)-O(2-) and Cu(II)/Cu(I)-O(2-) systems) and the formally mixed-valence Ag(II)/Ag(III)-F(-) and Ag(II)/Ag(I)-F(-) phases. For this purpose we perform electronic-structure computations for a number of structurally characterized binary and ternary Ag(I), Ag(II), and Ag(III) fluorides and compare the results with similar calculations for oxocuprate superconductors. Electronic levels in the vicinity of the Fermi level (x(2)-y(2) or z(2)) have usually strongly mixed Ag(d)/F(p) character and are Ag-F antibonding, thus providing the potential of efficient vibronic coupling (typical for d(9) systems with substantially covalent bonds). According to our computations this is the result not only of a coincidence in orbital energies; surprisingly the Ag-F bonding is substantially covalent in Ag(II) and Ag(III) fluorides. The electron density of state at the Fermi level (DOS(F)) for silver fluoride materials and frequencies of the metal-ligand stretching modes have values close to those for copper oxides. The above features suggest that properly hole- or electron-doped Ag(II) fluorides might be good BCS-type superconductors. We analyze a comproportionation/disproportionation equilibrium in the hole-doped Ag(II) fluorides, and the possible appearance of holes in the F(p) band. It seems that there is a chance of generating an Ag(III)-F(-)/Ag(II)-F(0) "ionic/covalent" curve crossing in the hole-doped Ag(II)-F(-) fluorides, significantly increasing vibronic coupling.

Real and Hypothetical Intermediate-Valence AgII/AgIII and AgII/AgI Fluoride Systems as Potential Superconductors

The chemistry of copper and silver in their higher oxidation states

Coordination chemistry in and of sulfur dioxide

Properties of lead difluoride are considered. Phase equilibria in PbF2–MFn systems (n = 1–5) and data on compounds and solid solutions formed in these systems are analysed. The characteristic features of phase diagrams of systems involving lead difluoride are discussed. Composites of PbF2 with other inorganic compounds hold promise as a basis for the design of new functional materials. The bibliography includes 331 references.

Lead difluoride and related systems

Reactions of MF2(M = Mg, Ni, Zn, Fe, Co, Cu, Cr, Ag, Cd, or Pb) with excess of SbF5 in anhydrous HF or SO2 at room temperature give adducts of composition MF2·2SbF5. Efforts to prepare similar adducts of the difluorides of Ca, Sr, and Ba led only to non-stoicheiometric compounds. Vibrational spectra and X-ray powder diffraction studies indicate that the Mg, Ni, and Zn compounds and the Fe, Co, and Cu compounds form two distinct isostructural triads. The remaining adducts have structures which differ from each other and from those of the two triads. A single-crystal X-ray study on AgF2·2SbF5 has shown that the crystals are triclinic, space group P, with unit-cell dimensions a= 5.224(1), b= 5.467(2), c= 8.779(2)A, α= 75.78(2), β= 89.02(2), γ= 65.29(2)°, and Z= 1. The Ag2+ ion has square-planar co-ordination with two Ag–F distances, 2.095(5) and 2.132(4)A. Two further F atoms at 2.431(3)A complete a distorted octahedron. Distorted [SbF6]– octahedra in the structure have four Sb–F distances between 1.830(4) and 1.875(3)A while two others are 1.942(4) and 1.965(4)A.

Metal(II) hexafluoroantimonates: preparation and characterization of MF2·2SbF5(M = Mg, Ni, Zn, Fe, Co, Cu, Cr, Ag, Cd, or Pb) and the X-ray structure determination of AgF2·2SbF5

Metal (II) hexafluoroarsenates: Preparation and vibrational spectroscopy of MF2·2AsF5 (M = Mg, Ca, Sr, Ba, Mn, Co, Ni, Cd, Hg, Pb) adducts [1]

Metal (II) hexafluoroarsenates: preparations and some properties of 2MF2·3AsF5 (M = Fe, Cu, Zn), MF2·AsF5 (M = Cr, Fe, Cu, Zn, Ag, Sn) and 2MF2·AsF5 (M = Ag, Sn)

Metal (II) hexafluoroarsenates: Thermal decomposition studies on the adducts MF2·2AsF5 (M = Mg, Ca, Sr, Mn, Co, Ni, Cd, Hg, Pb), 2MF2·3AsF5 (M = Fe, Cu, Zn) and MF2·AsF5 (M = Ag, Sn)

D. Gantar

Papers

Metal(II) hexafluoroantimonates: preparation and characterization of MF2·2SbF5(M = Mg, Ni, Zn, Fe, Co, Cu, Cr, Ag, Cd, or Pb) and the X-ray structure determination of AgF2·2SbF5

Metal (II) hexafluoroarsenates: Preparation and vibrational spectroscopy of MF2·2AsF5 (M = Mg, Ca, Sr, Ba, Mn, Co, Ni, Cd, Hg, Pb) adducts [1]

Metal (II) hexafluoroarsenates: preparations and some properties of 2MF2·3AsF5 (M = Fe, Cu, Zn), MF2·AsF5 (M = Cr, Fe, Cu, Zn, Ag, Sn) and 2MF2·AsF5 (M = Ag, Sn)

Metal (II) hexafluoroarsenates: Thermal decomposition studies on the adducts MF2·2AsF5 (M = Mg, Ca, Sr, Mn, Co, Ni, Cd, Hg, Pb), 2MF2·3AsF5 (M = Fe, Cu, Zn) and MF2·AsF5 (M = Ag, Sn)

Synthesis and characterization of hydrazinium (2+) tetrafluoroborate(III)