Dirhodium(II)-Catalyzed Sulfide Oxygenations: Catalyst Removal by Coprecipitation with Sulfoxides

The
dirhodium­(II) carboxylate complex Rh2(esp)2 (esp
= α,α,α′,α′-tetramethyl-1,3-benzenedipropanoate)
was shown to catalyze the sulfoxidation of organic sulfides using tert-butyl hydroperoxide as the oxidant. Due to the unique
structure of Rh2(esp)2 and its stable Rh2(II,II) catalyst resting state, the rhodium catalyst is able
to precipitate as a Rh2(esp)2–sulfoxide
complex following the reaction which makes separation of the catalyst
from the products very convenient. The precipitated Rh2(esp)2–sulfoxide complexes could be reused to catalyze
sulfide oxygenation reactions without considerable loss of activity.
Mechanistic studies suggest that the axial ligands fine-tune the redox
potential of the dirhodium­(II,II) compounds and determine the predominant
catalyst species in the oxidation reaction.