A Radical Chain: Mononuclear “Gold Only” Photocatalysis

We herein report an unprecedented reactivity of mononuclear gold catalysts acting as classical and at the same time active partners in a radical chain mechanism, whereby is only catalyst. The mechanism photo-induced photosensitizer-free “gold only”-catalyzed cross coupling was studied detail – experimentally theoretically based on reaction between arylboronic acids aryldiazonium salts. With systematic set stoichiometric experiments under various conditions analytic methods, we could show that this initiated by aryl formed presence blue LEDs MeOH. This enters catalytic cycle to oxidize gold(I) gold(II). Single electron transfer from gold(II) salt then gives cationic gold(III) complex formation chain-supporting which enabled start new oxidation without need for irradiation. At least every 432 cycles chain, chain-initiating has restart chain. Eventually, boronic acid activated BF4− anion transmetalate gold(III), reductive elimination delivers desired product.