The black, polymeric, product isolated from the reaction of Cu(II) salts wi
th MoS42 - has been shown to have some unexpected and unusual properties, i
.e. a stoichiometry of Cu1.6MoS4Xy. (X = Cl-, Br-, y approximate to 1; X =
SO42 -, y approximate to 0.5), reduction of the metal centres to Cu(I) and
Mo(V), the presence of S radical centres, and the absorption of ca. 2 mol O
-2. EXAFS spectra have also been recorded. The W anion WS42- behaves identi
cally. (C) 1998 Elsevier Science S.A. All rights reserved.