Synthesis and Characterization of Highly Water Soluble Ruthenium(II) and Osmium(II) Complexes Bearing Chelating Sulfonated N-Heterocyclic Carbene Ligands

The synthesis of highly water soluble ruthenium(II) and osmium(II) complexes based on chelating N-heterocyclic carbene (NHC) ligands bearing sulfonated side chains is reported. The complexes are easily accessible in very good yields via synthesis of silver-bis(NHC) complexes and subsequent reaction with [(p-cymene)MCl2](2) (M = Ru, Os). They express high thermal stability and are highly soluble in water (up to 400 mg/mL). The first structurally characterized Ru(II) complex bearing a chelating sulfonated ligand is presented.