The blue complex formed by reaction of hexaammineruthenium(II) dichloride and hydrochloric acid bas been characterized by analytical, spectroscopic, electrochemical, and chemical methods as a chlorobridged ruthenium(II)–ruthenium(III) dimer, [Ru2(NH3)6Cl4H2O]Cl. With hydrobromic acid the analogous complex [Ru2(NH3)6Br4H2O]Br is formed. Reactions of the complexes with ammonia and hydrohalic acids are reported.