Facile amino to pyridyl isomerization: pentaammineruthenium(II) walks the nicotinamide and isonicotinamide rings

When amido-bonded ruthenium(III) complexes of both nicotinamide and isonicotinamide are reduced, the resulting ruthenium(II) complexes, Ru[sup II](NH[sub 3])[sub 5](NHC(O)-3-Py)[sup +] and Ru[sup II](NH[sub 3])[sub 5](NHC(O)-4-Py)[sup +], undergo rapid protonation, followed by intramolecular isomerization (k[sub 4-Py] = 9.6 s[sup [minus]1] at 25[degree]C) to the pyridyl-bonded forms. The authors believe these rearrangements proceed via [eta][sup 2]- arene-bonded intermediates in a walk of the aromatic ring as has been found for related osmium(II) complexes.