Metallacarboranes as photoredox catalysts in water

Metallacarboranes with a Greek letter theta shape like [Co(C 2 B 9 H 11 ) 2 ] - have been tested, for the first time, as efficient photoredox catalysts in the oxidation of aromatic and aliphatic alcohols in water. The efficiency displayed by them is linked to their high solubility in water, their high oxidizing power ( Co 4+/3+ ), and their absence of fluorescence upon excitation, among others. In most of the studied examples, using a catalyst load of 0,4 mol %, high yields near 90-95% have been obtained, with selectivity values >99%. By reducing the catalyst load to 0,01 mol %, quantitative conversion of reactants into products have been achieved, in some cases over 99% yield, exhibiting the catalyst high efficiency to reach TON=10000, and proving that a higher yield is achieved with 45 times less concentrated catalyst. Metallacarboranes can be recovered easily by precipitation upon the addition of [NMe 4 ]Cl. Further a postulated pathway for the photoredox catalyzed oxidation of alcohols has been proposed.