George M. Lucier

HIGH YIELD ROOM TEMPERATURE SYNTHESES OF KAGF4 AND AGF3 AND THE PREPARATION AND UNIT CELL OF LIAGF4

Abstract AgF 2 dissolves at ∼ 20°C in liquid anhydrous hydrogen fluoride (aHF), containing either LiF or KF, with sunlight or ultraviolet (UV)-irradiated F 2 . Concentrated KF-aHF solutions quickly give a nearly quantitative conversion to KAgF 4 . Preparation of LiAgF 4 is less efficient, but it can be prepared in high purity. It is isomorphous with LiAuF 4 , and has a monoclinic unit cell: a = 4.87 (1)_; b = 5.93 (1) ; c = 10.08 (1) A; β = 93.0(1)°; V = 291 (1) A 3 ; z = 4. KHF 2 impurity in KAgF 4 can be removed as KPF 6 with PF s at 0°C. Preparation of AgF 3 , with minimum contamination by Ag 3 F 8 , is achieved at 0°C using GeF 4 as F − acceptor. The high solubility of the salt K 2 GeF 6 makes this possible.

Some chemistry of high oxidation state transition metal fluorides in anhydrous HF

Abstract The salt AgFIrF6 ( AgIrF 6 + 1 2 F 2 in AHF) is isostructural with AgFAsF6. Failure to prepare AgFOsF6 (AgOsF6 + F2 → AgF2 + OsF6) indicates that the one-dimensional chain cation (AgF)nn+ takes the electron from OsF6−. The Ag(solv)2+ ion oxidizes IrF6− to IrF6 and at −78 °C in AHF, O2 to O2+ (O2 + Ag2+ + 2AsF6− → O2+AsF6− + AgAsF6). This reaction is negligible at ∼20 °C because of the loss of translational entropy that accompanies the formation of the crystalline products. Dissolution of AgF3 in AHF with A (A = AsF5, SbF5 or BiF5) gives a solution {Ag(solv)III} which oxidizes PtF6− or RuF6− to MF6 and O2 to O2+. K2NiF6 in AHF below −60 °C with greater than threefold molar excess of BF3 yields yellow-brown solutions {Ni(solv)IV} which also oxidize PtF6− or RuF6− to MF6. The species Ag(solv)III and Ni(solv)IV in AHF are oxidizers of unsurpassed power.

Structural and magnetic properties of some AgF+ Salts

New salts of the one-dimensional chain-cation (Ag−F)nn+ have been prepared, the structural and magnetic properties of which indicate that they are metallic. A single-crystal X-ray structure analysis of AgFBF4 has established a linear cationic chain, the two Ag−F interatomic distances, at 296 K, being 2.002(3) and 2.009(3) A. Magnetic susceptibility measurements on the poweder from 6 to 280 K show an approximately temperature-independent paramagnetism (χM∼180×10−6 emu mole−1) with no evidence of a Peierls transition in that range. Although the previously known salt, AgFAsF6, has a kinked cationic chain (with, at 166 K, Ag−F−Ag=143.1(1)o, F−Ag−F=175.8(1)o, Ag−F=1.994(2) and 2.001(2) A), it also exhibits temperature-independent paramagnetism from 280 down to 63 K, but a sharp drop in susceptibility below that temperature may signify a Peierls transition. AgFAuF6, which is probably isostructural with AgFAsF6, is similar to it magnetically. The salt AgFAuF4 probably contains a linear cationic chain, since it is isostructural with CuFAuF4, but the salt Ag(AuF4)2, like its relative Ag(AgF4)2, is a magnetically dilute paramagnet, the magnetic susceptibility of which departs very little from the Curie law between 6 and 280 K.

The room temperature conversion of nickel difluoride to hexafluoronickelate(IV) salts of alkali cations

Abstract NiF 2 was oxidized at ~20 °C, to NiF 6 2− by sunlight or ultraviolet light-irradiated F 2 in liquid anhydrous hydrogen fluoride (aHF) containing alkali hydrofluorides AF(HF) x . Quantitative formation of NiF 6 2 can be achieved with strongly basic solutions (e.g., KF:HF molar ratio ~ 1:4). Li 2 NiF 6 , which was previously unknown, is the least aHF soluble of the alkali NiF 6 2 salts, and was prepared in high purity.