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.