Bimetallic iron–iron and iron–zinc complexes of the redox-active ONO pincer ligand

Abstract

Synthetic and magnetic studies of homo- and heterobimetallic complexes of the redox-active ONO pincer ligand.

Catalytic Synthesis of N-Heterocycles via Direct C(sp3)–H Amination Using an Air-Stable Iron(III) Species with a Redox-Active Ligand

“…The iron–ligand bond lengths, angles, and interatomic distances within the NNO moieties are very similar for both molecules and suggestive of the ISQ ligand oxidation state. 14,18−20 The iron–ligand bond lengths in complex 2 (average bond distances: Fe–O 1.928 Å, Fe–N imino 1.884 Å, Fe–N pyridyl 1.963 Å) are slightly shorter than those in heteroleptic complex 1 (Fe–O 1.957 Å, Fe–N imino 2.014 Å, Fe–N pyridyl 2.102 Å). On the contrary, the ligand-based interatomic distances in 2 (average bond distances: C–O 1.320 Å, C–N imino 1.368 Å) are slightly longer than those in complex 1 (C–O 1.281 Å, C–N imino 1.339 Å).…”

“…The geometry around iron (τ of 0.52) is intermediate between trigonal bipyramidal and square pyramidal. The iron–ligand bond lengths (Fe–O 1.9572(10); Fe–N 2.0136(12) Å) as well as ligand-based interatomic distances (O1–C1 1.2809(17); N1–C6 1.3390(17) Å) are characteristic of the ISQ ligand oxidation state. ,− A metrical oxidation state value of −0.69 (±0.04) was determined for the NNO ISQ ligand of 1 . Density functional theory (DFT) calculations (B3LYP, def2-TZVP) show a broken-symmetry S = 2 spin state (⟨ S 2 ⟩ = 6.8) as the ground state (see Supporting Information).…”

Mixed‐Valence o‐Iminobenzoquinone and o‐Iminobenzosemiquinonate Anion Radical Complexes of Cobalt: Valence Tautomerism

“…The X‐ray bond parameters in conjunction with the DFT calculations predicted a contribution of both L SPh ISQ · – and L SPh IQ states to the ground electronic states of 1 – 5 , which are defined as ligand‐based mixed‐valence complexes of types trans ‐[Co II (L SPh ISQ · – )(L SPh IQ )X]. The delocalized states are defined as Robin–Day Class III states of types trans ‐[Co II (L SPh ISQ 0.5 · – ) 2 X]. The investigation revealed that [ 1 – 5 ] exhibit different electronic states in solutions and solids because of tautomeric equilibria of types trans ‐[Co II (L SPh ISQ 0.5 · – ) 2 X] ⇌ trans ‐[Co III (L SPh ISQ · – ) 2 X]; [ 1 – 5 ] + and [ 1 – 5 ] – in solutions establish tautomeric equilibria of types [Co III (L SPh ISQ 0.5 · – ) 2 X] + ⇌ [Co II (L SPh IQ ) 2 X] + and [Co III (L SPh ISQ 0.5 · –1.0– ) 2 X] – ⇌ [Co II (L SPh ISQ · – ) 2 X] – .…”

“…Transition‐metal complexes L OO H 2 , L NO H 2 , and L NN H 2 exist in three different electronic states, as depicted in Scheme , within a relatively small potential range. These features of such redox non‐innocent ligands open up the opportunity to build ligand‐based mixed‐valence complexes of transition‐metal ions …”

Structural Differences and Redox Properties of Unsymmetric Diiron PDIxCy Complexes

“…Differing ligand environments, correlated with distinct electronic properties, allow each metal center to adopt a unique role in the overall reaction , . Accordingly, a number of bio‐inspired, unsymmetric complexes ― not only of iron, but with other metals ― have been reported in recent years, which merge unique coordination environments …”