Mechanistic Insights into the C–S Bond Breaking in Dibenzothiophene Sulfones

The reactivity of Grignard reagents in the presence of nickel catalysts is known to be highly efficient in the deoxydesulfurization of dibenzothiophene sulfone (DBTO2), 4-methyldibenzothiophene (4-MeDBTO2), and 4,6-dimethyldibenzothiophene (4,6-Me2DBTO2), to yield sulfur-free biphenyls via cross-coupling reactions. However, the mechanistic details involved in the process remained unknown. In this report the reactivity of [(dippe)­Pt­(μ-H)]2 with DBTO2 turned out to be catalytically less efficient compared with [(dippe)­Ni­(μ-H)]2, but the first allowed the isolation and full characterization of several reaction intermediates, such as [(dippe)­Pt­(κ2-C,S-DBTO2)]. It was demonstrated that this is a key intermediate in all the deoxydesulfurization reactions of the above-mentioned aromatic sulfones (DBTsO2).