Untersuchung hochreaktiver Organonickel-Komplexe mit Bedeutung für Nickel-katalysierte C-C-Kupplungsreaktionen

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The mechanistical investigation on single electron transfer induced C-C coupling reaction based on nickel catalysts started in two previous project will be extended/ prolonged. New mono- and binuclear organonickel model complexes carrying bi- or tridentate diimine (diazene) ligands) will be synthesised and their spectroscopy and electrochemistry (including spectroelectrochemistry) thoroughly investigated. one focus will be put on the investigation of the supposed disproportionation-transmetallation reaction of the reduced nickel species [(N^N)Ni(R)]• yielding [(N^N)Ni(R)2] and [(N^N)Ni] which finally leads to unwanted homo coupling. The other focus will be put on the oxidative addition reaction of organohalides R’X with the reduced species [(N^N)Ni(R)]• (including cyclometallated [(N^N^R)NiX] and „unsymmetrical“ [(N^N’)Ni(R)X] derivatives) yielding formal Ni(III) complexes [(N^N)Ni(R)(R‘)X]•. The spin delocalisation in both types of radical complexes {formally Ni(I) and Ni(III)} between chelate ligands, organo coligands and the metal will be studied using a combination of spectroelectrochemistry (EPR- and UV-Vis-NIR spectroscopy) and quantum chemical calculations.