Merocyanine-like chromophores as ligands for catalytic active metals of group VIII

Nickel and palladium complexes that contain merocyanine-like 4H-imidazoles as ligands have been synthesized in good yields. The complexes were characterized by elemental analyses, mass spectrometry, H-1 NMR, C-13 NMR spectroscopy and in the solid state by single crystal diffraction analyses. The new palladium complexes of type 4 can be regarded as new functional dyes as well as deeply coloured and redox active metallacycles that display catalytic activity. In contrast to parent compounds 2, the palladacycles of type 4 show two well-separated reductions that are fully reversible. The values of semiquinone formation constants of derivatives 4 (between 10(11) and 10(12)) are only somewhat lower than those reported for similar boracycles. (c) Wiley-VCH Verlag GmbH & Co. KGaA.