Pyridyl to amido and amido to pyridyl isomerisation in an isonicotinamide complex of ruthenium(III)

Abstract

The reaction of [Ru^III(edta)(H₂O)]^–(edta = ethylenediamine-N,N,N′,N′-tetraacetate) with isonicotinamide (isna) was studied spectrophotometrically at different pH (6–10), isonicotinamide concentrations and ionic strengths. The pyridyl-N-co-ordinated complex [Ru(edta)(isna)]^– is stable at low pH (6.0), but undergoes intramolecular isomerisation at high pH (9.6) to yield the amido-N-co-ordinated [Ru(edta)(isna)]^2–. Upon acidification, the amido-N-bonded species isomerises back to the pyridyl-N-co-ordinated isomer.