A Diruthenium Complex of an N ‐Pyridyl‐ o ‐aminophenol Derivative: A Route to Mixed Valency

An N ‐pyridyl‐ o ‐aminophenol derivative that stabilises mixed‐valence states of ruthenium ions is disclosed. A diruthenium complex, [(L IQ 0 )Ru 2 Cl 5 ] ⋅ MeOH ( 1⋅ MeOH) is successfully isolated, in which L IQ 0 is the o ‐iminobenzoquinone form of 2‐[(3‐nitropyridin‐2‐yl)amino]phenol (L AP H 2 ). In 1 , L IQ 0 oriented towards one ruthenium centre is a non‐innocent NO‐donor redox ligand, whereas another oriented towards another ruthenium centre is an innocent pyridine‐donor redox ligand. Complex 1 is a diruthenium(II,III) mixed‐valence complex, [Ru II (L IQ 0 )(μ‐Cl) 2 Ru III ], with a minor contribution from the diruthenium(III,III) state. [Ru III (L ISQ .− )(μ‐Cl) 2 Ru III ] contains L ISQ .− , which is the o ‐iminobenzosemiquinonate anion radical form of the ligand. Complexes 1 − and 1 + are diruthenium(II,II), [Ru II (L IQ 0 )(μ‐Cl) 2 Ru II ], and diruthenium(III,III), [Ru III (L IQ 0 )(μ‐Cl) 2 Ru III ], complexes, respectively, of L IQ 0 . Complex 1 2− is a diruthenium(II,II) complex of the o ‐iminobenzosemiquinonate anion radical (L ISQ .− ), [Ru II (L ISQ .− )(μ‐Cl) 2 Ru II ], with a minor contribution from the diruthenium(III,II) form, [Ru III (L AP 2− )(μ‐Cl) 2 Ru II ]. Complex 1 2+ is a diruthenium(III,IV) mixed‐valence complex of L IQ 0 , [Ru III (L IQ 0 )(μ‐Cl) 2 Ru IV ]. Complexes 1 and 1 2+ exhibit inter‐valence charge‐transfer transitions at λ =1300 and 1370 nm, respectively.