No abstract

PF3 and CO react with CuAsF6 in SO2 solution to form 1:1 addition compounds, the vibrational spectra of which are consistent with the formulations [CuPF3]+[AsF6]− and [CuCO]+[AsF6]−. The latter has a v[CO] stretch at 2180 ± 5 cm−1, the highest yet observed for a monocarbonyl.

Passivating films formed on lithium in 1M LiAsFd2-methyltetrahydrofuran electrolyte have been analyzed using the AC impedance technique. The complex plane impedance analysis of the lithium electrode under polarization show two types of behavior. The first type is observed for discharge overpotentials less than 250 inV. In this case, the electrode impedance decreases with increasing anodic overpotentials. The second type is observed for overpotentials greater than 250 mV. The electrode impedance in the second case increases continuously with increasing voltage. Critical values for current densities which would allow cell cycling without a major deterioration of the electrochemical properties of the lithium electrode have been assessed. In addition, mechanical and electrochemical surface treatment methods have been studied in order to determine their effect on the initial AC impedance parameters of lithium electrodes in 1M LiAsFd 2-MeTHF electrolytes.

Lithium hexafluoroarsenate/2-methyl tetrahydrofuran electrolytes have been prepared, purified, and evaluated using half-cell galvanostatic lithium cycling, cyclic voltammetry, plus colorimetric, gas chromatographic, and UV absorption techniques. Superior electrolytes have been prepared yielding reproducible cycling efficiencies in excess of 97%. Static aging trials at ambient temperature clearly demonstrate deterioration in cycling performance with time. This decline in performance is related to electrolyte degradation, possibly arising from the formation of peroxides. However, studies of various battery testing regimes on 1M LiAsFd2Me-THF electrolyte support the system's battery potential with respect to both rate capability and shelf-life characteristics.

Solid Se,(AsF,), reacts with C2F4 at room temperature to form (CzF5)zSez ( x = 2 or 3). Se8(SbzFll)2 gives similar products on reaction with C2F4 at 100 "C. In SO, solution Se8(AsF6), and C,F, give mainly (C,F,)2Se, and C2F5Se,CF,C[O] F ; the latter was characterised by its lSF n.m.r. and mass spectrum.VARIOUS polycations of Group VI have been prepared and characterizedl and the structure of these and related compounds discussed.l-3 However, their chemical properties have not been systematically investigated.As part of such a s t ~d y , ~ solid s,(AsF6), was allowed to react with tetrafluoroet hylene a t ambient pressure and temperature to yield (C,E',),S, ( x = 2-6).5 A reaction intermedipte with C2F4 interacting with the weak tramring sulphur-sulphur bond in &,+, was suggested.6 The structure of SeB2+ is very much like that of sS2+, and it was of interest to determine whether a similar reaction yielding the corresponding bis(perfluoroethy1)polyselenides would occur. The selenium system is probably simpler in that SeS2+ in the solid state, and in solution, is diamagnetic,'.8 and that a species analogous to S,+, which exists in equilibrium with S,2+ in ~o l u t i o n , ~-~~ has not been observed. The results reported herein involve the reaction of tetrafluoroethylene with Se,(AsF6), and Ses(Sb,F,,) 2' EXPERIMENTAL A@aratus.-All volatile compounds mere manipulated in a Pyrex glass vacuum line fitted with ' Rotaflo ' valves