The well known blue solutions of ruthenium(II) have been reinvestigated. The formulation as RuII species is confirmed by coulometry, and stable blue salts, of the (o-phenylenedimethylene)bis(triphenylphosphonium)dipositive cation, have been isolated; stable salts were also obtained with [bipy3M]2+(M = Fe and Ru, bipy = 2,2′-bipyridyl). All three appear to contain the cluster anion Ru5CI122–. The e.s.r. spectra of the blue solutions and of the isolated anion are identical but the paramagnetism is unusually low. Green salts which appear to contain the anion RuCI3–, and which may also contain the cluster [Ru4CI12]4–, have been obtained.