A mixed-valence compound with one unpaired electron delocalized over four molybdenum atoms in a cyclic tetranuclear ion

The first oxidation of a species derived from a compound having two linked, quadruply-bonded Mo2 units has been performed and [[cis-Mo2(DAniF)2]2(mu-Cl)4]PF6, 2, has been isolated and characterized in many ways; it has one unpaired electron and a fully delocalized structure where the Mo-Mo distances increase from 2.1191(4) A in the reduced species to 2.1453(3) A in 2 and the Kc of 1.3 x 10(9) is three orders of magnitude larger than that of the Creutz-Taube ion.