The preparation of copper(II) and copper(I) salts in acetonitrile using group VA and VB pentafluorides

Copper(II) fluorine reacts with the pentafluorides, TaF₅, PF₅, and AsF₅, in acetonitrile to give solvated Cu^II, hexafluoroanion salts. These react with copper metal to give the corresponding Cu^I compounds. Similar reactions occur between AsF₅ and silver(I) or thallium(I) fluorides, but silver(II) fluoride reacts with MeCN, and Ag^I hexafluoroarsenate is formed. PF₅ oxidises Cu slowly in MeCN to give Cu^I hexafluorophosphate, but AsF₅ has no oxidising ability towards metals in MeCN. Spectroscopic data for Cu(MF₆)₂·5MeCN and Cu(MF₆)·4MeCN (M = Ta or P) are discussed.