Ann Prescott

Redox reactions involving rhenium and uranium hexafluorides, a convenient synthesis of β-uranium pentafluoride

Abstract Rhenium and uranium hexafluorides oxidise elemental iodine in iodine pentafluoride at ambient temperature to give the I 2 + cation. With UF 6 an additional reaction occurs to give β-uranium pentafluoride as one product, β-UF 5 is soluble in acetonitrile without disproportionation and is also formed from the reduction of UF 6 by MeCN. Copper, cadmium, and thallium metals are oxidised by ReF 6 in MeCN giving Cu I , Cd II , and Tl I hexafluororhenates(V) but the reactions are complicated by reaction between ReF 6 and the solvent.

Oxidation of metals by molybdenum and tungsten hexafluorides in acetonitrile

The metals Ag, Tl, Pb, Zn, Cd, Hg, Mn, Co, Ni, and Cu are oxidised by molybdeninn and tungsten hexafluorides in acetonitrile solution at ambient temperature. The products are solvated metal cations, the counter anions being hexafluoro-molybdate(V) or -tungstate(V). MoF6 Oxidises Ag and Tl to AgII and TlIII respectively whereas AgI and TlI are formed with WF6. Thus MoF6 is the stronger oxidising agent.

The oxidising and fluoride ion acceptor properties of uranium hexafluoride in acetonitrile

Metallic copper, cadmium, and thallium are oxidised by uranium hexafluoride in acetonitrile at ambient temperatures to give solutions of copper(II), cadmium(II), and thallium(III) hexafluorouranates(V). After removal of solvent, these salts were obtained as solvates. Copper(II) fluoride reacts with uranium hexafluoride in acetonitrile to give copper(II) heptafluorouranate(VI).

Formation of metal heptafluorotungstates(VI) in acetonitrile

Thallium(I) and copper(II) fluorides react with tungsten hexafluoride in acetonitrile and the soluble adducts TIF·WF6 and CuF2·2WF6·5MeCN are isolated from solution. The adducts are formulated as metal heptafluoro-tungstates(VI). The hexafluorotungstate(V) anion behaves as a fluoride-ion donor in MeCN, reacting with WF6 to give the WF7– anion as one product.

Oxidising behaviour of molybdenum and tungsten hexafluorides

Silver metal reacts with Mo6F or WF6 in acetonitrile to give [AgII(NCMe)4][MoVF6]2 or [AgI(NCMe)2]-[WVF6] respectively; the results clearly show the greater oxidising power of MoF6 as compared with WF6.