Catalytic Dehalogenation of Aryl Halides via Excited State Electron Transfer from the Co(I) State of B12 Complex

Reductive dehalogenation of aryl halides, bromobenzonitrile and iodobenzonitrile by the photo-excited B12 complex with the labile Co(I) oxidation state under anaerobic conditions was reported for the first time. A sub-pico second time-resolved spectroscopic analysis showed that the excited state of the B12 complex, *Co(I), has a 280 ps lifetime and the rate constants of electron transfer to the reactants (kET) are 3.6 × 109, 3.3 × 109, and 1.4 × 109 M−1s−1 for iodobenzonitrile, bromobenzonitrile, and chlorobenzonitrile, respectively. Reductive dehalogenation of aryl halides, bromobenzonitrile and iodobenzonitrile by the photo-excited B12 complex with the labile Co(I) oxidation state under anaerobic conditions was reported for the first time. A sub-pico second time-resolved spectroscopic analysis showed that the excited state of the B12 complex, *Co(I), has a 280 ps lifetime and the rate constants of electron transfer to the reactants (kET) are 3.6 × 109, 3.3 × 109, and 1.4 × 109 M−1s−1 for iodobenzonitrile, bromobenzonitrile, and chlorobenzonitrile, respectively.