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

Abstract

An N‐pyridyl‐o‐aminophenol derivative that stabilises mixed‐valence states of ruthenium ions is disclosed. A diruthenium complex, [(LIQ0)Ru2Cl5]⋅MeOH (1⋅MeOH) is successfully isolated, in which LIQ0 is the o‐iminobenzoquinone form of 2‐[(3‐nitropyridin‐2‐yl)amino]phenol (LAPH2). In 1, LIQ0 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, [RuII(LIQ0)(μ‐Cl)2RuIII], with a minor contribution from the diruthenium(III,III) state. [RuIII(LISQ.−)(μ‐Cl)2RuIII] contains LISQ.−, which is the o‐iminobenzosemiquinonate anion radical form of the ligand. Complexes 1− and 1+ are diruthenium(II,II), [RuII(LIQ0)(μ‐Cl)2RuII], and diruthenium(III,III), [RuIII(LIQ0)(μ‐Cl)2RuIII], complexes, respectively, of LIQ0. Complex 12− is a diruthenium(II,II) complex of the o‐iminobenzosemiquinonate anion radical (LISQ.−), [RuII(LISQ.−)(μ‐Cl)2RuII], with a minor contribution from the diruthenium(III,II) form, [RuIII(LAP2−)(μ‐Cl)2RuII]. Complex 12+ is a diruthenium(III,IV) mixed‐valence complex of LIQ0, [RuIII(LIQ0)(μ‐Cl)2RuIV]. Complexes 1 and 12+ exhibit inter‐valence charge‐transfer transitions at λ=1300 and 1370 nm, respectively.

Ni(ii) complexes of a new tetradentate NN′N′′O picolinoyl-1,2-phenylenediamide-phenolate redox-active ligand at different redox levels

“…In the search for appended additional coordinating groups, many interesting 2-aminophenolate ligand systems have been synthesized by us 11 and others. 12–20 In this work, our attention has been directed to 1,2-phenylenediamine spacer H 4 L 1 (Fig. 1).…”

“…This redox-active ligand is unique in the sense that it has three coordinating units, including two redox-active components: (i) a pyridine-2-carboxamido part with strong σ-donating amido- N to stabilize the high-valent metal ion, 21 (ii) a redox-active 1,2-phenylenediamido part 10 and (iii) a redox-active 2-aminophenolate part. 2 c,f ,11–20 Understandably, the net effect is expected to be quite exciting and hence worth investigating. Research by our group explores the unique electronic interactions accessible to transition metal complexes with redox-active ligands, especially in cases where the observed redox processes are attributed explicitly to the redox properties of the ligand.…”