Theoretical study of the reaction of 7,8-dicarba-nido-undecaborane with S-nucleophiles in the presence of mercury(ii) chloride

The mechanism of the reaction of 7,8-dicarba-nido-undecaborane potassium salt with thioethers was studied for the first time within the framework of the electron density functional theory. The regiospecifity of the reactions involving dimethyl sulfide and methyl S-methyl-N-trifluoroacetyl-(R)-cysteinate at position B(10) of nido-carborane was substantiated by quantum chemical calculations. Evidence was obtained that the reaction of 7,8-dicarba-nido-undecaborane potassium salt with S-nucleophiles proceeded more actively in the presence of mercury(ii) chloride. The structure was optimized and the energies of intermediates were calculated at the final Toluene-CPCM-B3LYP-D3-gCP/def2-TZVP (Hg LANL2TZ) level of the theory. It was found that the key step of the reaction is the synchronous process of the B(10)—S bond formation and the hydrogen abstraction from the B(10) vertex proceeding with the participation of the mercury atom from the nido-carborane-based intermediate π-complex.