Abstract:
Amidophenolate based non–innocent ligands and their corresponding transition metal (M) complexes are very effective for enzymic mimicking, catalytic C–C cross coupling reaction, –CF3 group transferring agent, C–O/N/S bond activation, valence tautomeric species formation, synthesis of M–quinone species, etc. Thus, a few non–innocent ligands with two orthogonally placed aminophenol units were designed and synthesized by placing a common chalcogen (O, S, Se and Te) bridge between two H2LAP [N(2–hydroxy–3,5–di–tert–butyl phenyl) aniline] ligand units. The sulfur bridged ligand H4LS(AP/AP) provided an unprecedented octahedral complex, 2E, where one of the two coordinated amidophenolate units was present in its two electron oxidized iminoquinone {[IBQ]0} form and other was in its one–electron oxidized iminosemiquinone {[ISQ]•1–} form. The oxygen bridged ligand H4LO(AP/AP) provided a mononuclear octahedral cobalt complex 3A by two set of successive homolytic Caryl–Obridge bond breaking and homolytic Co–Obridge bond formation. Complex 3A showed solvent and solid phase thermal tautomerization and the solid phase tautomeric conversion depends upon the availability of the lattice solvent within the crystalline matrix. An unprecedented one–step synthesis of Cu(II)–bis(iminoquinone) complex using amidophenolate based ligand has been established by using non–innocent ligand H2LAP(o–NO2–OPh) and the Cu(II)–complex mimicked the function of coenzyme ubiquinone.
