Structural, magnetochemical and electrochemical studies of dinuclear complexes containing the [VVO]2, [VIVO]2, Cr2III, Mn2III and Fe2III cores of a potentially pentadentate phenol-containing ligand with (O,N,O,N,O)-donor atoms

Dinuclear complexes [L2Fe2III] (1), [L2Mn2III] (2a), [L2Mn2III(THF)(2)] (2b), [L2Cr2III] (3), [L((VO)-O-IV)(2)(OCHMe2)] (4) 2 2 and [L-2((VO)-O-V)(2)] (5) with a pentadentate phenol-containing ligand H3L (= C6H2(CH3)(OH){[C(CH3)(3)](2)(OH)NCH}(2)) bearing the N2O3 donor atoms have been synthesized and the X-ray structures of 1, 2b, 4 and 5 are reported. The compounds were characterized by IR, UV/Vis and Mossbauer spectroscopy, mass spectrometry, electrochemical and variable-temperature (2-295 K) magnetic susceptibility measurements. Analysis of the susceptibility data demonstrates anti-ferromagnetic interactions between the metal centers establishing diamagnetic ground states for complexes 1-4. The electrochemical results suggest the generation of ligand-centered oxidation processes attributable to the phenoxyl radicals, rather than the formation of unusually high oxidation states at the central metal centers. The ligand H3L has the potential to act in a multidentate fashion as evidenced by the X-ray structures of 2b and 5. In compound 2b the central phenolate oxygen of the p-cresol ring does not function as a bridging atom between two manganese centers, whereas in 5 the ligand is tetradentate with one noncoordinating nitrogen atom. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.