O,N-Coordinated o-iminobenzoquinone and o-iminobenzosemiquinonato(1–) ligands in complexes of Ni(II), Co(III) and Fe(III)

Octahedral complexes of the type [M(tren)(LIBQ)]n+ or [M(tren)(LISQ)]n+(tren = tris(2-aminoethyl)amine; LIBQ=oiminobenzoquinone, (LISQ)1–=o-iminobenzosemiquinonate(1–) 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 [NiII(tren)(LIBQ)](PF6)2(1), green [NiII(tren) (LISQ)](ClO4)(2), brown [CoIII(tren)(LISQ)](ClO4)2·0.5CH3OH·0.5H2O (3), [FeIII(tren)(LISQ)](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 M?ssbauer spectroscopy. Temperature-dependent magnetic susceptibility measurements (2–290 K) reveal that 1 possesses an S= 1, 2 an S= 3/2, 3 an S=½, and 4 an S= 0 ground state. The metrical details of O,N-coordinated (LAP-H)2–, (LISQ)1–, and (LIBQ)0 ligands are clearly established. (LAP-H)2– represents the aromatic dianion o-iminophenolate.