Arene ruthenium complexes [(η 6-arene)Ru(sacc) 2(OH 2)] (arene = para-cymeme, benzene) containing an aqua and two saccharinato ligands have been synthesized from [(η 6-arene)RuCl 2] 2 and sodium saccharinate in a water-ethanol mixture (1:1). The aqua complex [(η 6-MeC 6H 4Pr i )Ru(sacc) 2(OH 2)] reacts with acetonitrile to give the acetonitrile complex [(η 6-MeC 6H 4Pr i )Ru(sacc) 2(NCMe)]. The corresponding benzene derivative [(η 6-C 6H 6)Ru(sacc) 2(NCMe)] was obtained from [(η 6-C 6H 6)RuCl 2] 2 and saccNa in an acetonitrile-methanol mixture (1:1). All new complexes show a piano-stool geometry with two mono-hapto nitrogen-bonded saccharinato ligands in addition to a H 2O or MeCN ligand. All complexes of the type [(η 6-arene)Ru(sacc) 2(OH 2)] and [(η 6-arene)Ru(sacc) 2(NCMe)] were found to catalyze the oxidation of secondary alcohols with tert-butyl hydroperoxide (Bu t OOH) to give the corresponding ketones in aqueous solution.