O,N-coordinated o-iminobenzoquinone and o-iminobenzo-semiquinonato(1-) ligands in complexes of Ni(II), Co(III) and Fe(III)

Octahedral complexes of the type [M(tren)(L^IBQ)]ⁿ⁺ or [M(tren)(L^ISQ)]ⁿ⁺ (tren = tris(2-aminoethyl)amine; L ^IBQ = o-iminobenzoquinone, (L^ISQ)^1- = o-iminobenzosemiquinonate(1-)π radical, M = Ni, Co, Fe) have been prepared by the reaction of equimolar amounts of 2-anilino-4,6-di-tert-butylphenol, tris(2-aminoethyl)amine, M(CH₃CO₂)₂· 4H₂O (M = Ni, Co) or FeCl₂·4H₂O in CH₃OH containing 2 equivalents of NEt₃ and air. The following complexes were isolated and characterized by X-ray crystallography: red-black [Ni^II(tren)(L^IBQ)](PF₆)₂ (1), green [Ni^II(tren)(L^ISQ)](ClO₄) (2), brown [Co^III(tren)(L^ISQ)](ClO₄)₂·0. 5CH₃OH·0.5H₂O (3), [Fe^III(tren)(L ^ISQ)](ClO₄)₂·0.5CH₃OH· 0.5H₂O (4). Their electrochemistry has been studied and the oxidized and reduced species have been characterized by UV-vis, EPR and Mössbauer spectroscopy. Temperature-dependent magnetic susceptibility measurements (2-290 K.) reveal that 1 possesses an S= 1, 2 an S= 3/2, 3 an S= 1/2, and 4 an S = 0 ground state. The metrical details of O,N-coordinated (L^AP-H) ^2-, (L^ISQ)^1-., and (L^IBQ) ⁰ ligands are clearly established. (L^AP-H)^2- represents the aromatic dianion o-iminophenolate.