Synthesis, chemical reactions and redox properties of ruthenium complexes of a tetradentatebis chelating ligand, 2,2′-azobis(pyridine)

The use of silver (I) assisted metal exchange reaction for the synthesis of mononuclear ruthenium (II) complexes of a tetradentate bridging ligand, 2,2′-azobis(pyridine) (L1) is elaborated. This route has been successfully employed for the direct synthesis of RuCl2(L1)2 (2); [Ru(L1)3](ClO4)2·H2O (3) from RuCl3·3H2O and for the mixed ligandtris chelates of general composition [Ru(L1)n(L)3−n]2+ (n=0–3;L=neutral N,N donors: 2-(phenylazo)pyridine (L2), 2,2′-bipyridine(L3)). The preparation of [Ru(OH2)2(L1)2]2+ (7) from 2 is also described. The diaquo complex,7, is chemically reactive and undergoes anation, solvolysis and substitution reactions instantaneously with different nucleophiles. All the reactions, described above, occur smoothly and the yields of the products are high. The composition and identities of the complexes are established from their elemental analyses and spectral data. The redox properties of the compounds have been examined. Metal oxidation responses occur at very high positive potentials. Successive reductive responses occur on the negative of the SCE.