Sulfonate- or carboxylate-functionalized N-heterocyclic bis-carbene ligands and related water soluble silver complexes

New N-heterocyclic carbene ligand precursors {H2C(HTz(R))(2)} and {H2C(HIm(R))(2)} (HTz = 1,2,4-triazole; HIm = imidazole; R = PrSO3 or EtCOO) were obtained starting from the compounds bis(1,2,4-triazol-1-yl)methane and bis(imidazol-1-yl)methane. The related silver(I) carbene complexes were prepared in degassed water solution by treatment of the triazolium or imidazolium species with Ag2O, resulting in well-characterized and water soluble bimetallic complexes of general formula {Na-2[H2C(Tz(R))(2)](2)Ag-2} and {Na-2[H2C(Im(R))(2)](2)Ag-2}. In these metallacycles every silver atom is coordinated to two triazolin-or imidazolin-2-ylidene rings, belonging to two different dicarbene units.