Sulfonyl fluoride activation via S-F and C-S bond cleavage by a Ni(0) bis-bidentate N- heterocyclic carbene complex

This work investigates possible mechanisms and intermediates in the reactivity of p-toluenesulfonyl fluoride with a new bidentate N-heterocyclic carbene (NHC) nickel complex, (MesNHC2oXy)Ni(COD) (Mes = 2,4,6-trimethylphenyl, oXy = ortho-xylyl, COD = cyclooctadiene). (MesNHC2oXy)Ni(COD) was synthesized from the corresponding bis(imidazolium) salt precursor, [MesNHC2oXy][Br]2, and both were structurally characterized. (MesNHC2oXy)Ni(COD) reacts with one equivalent of p-toluenesulfonyl fluoride to furnish (MesNHC2oXy)Ni(2-SO2), HF, and ½ equivalent of 4,4’-dimethylbiphenyl. (MesNHC2oXy)Ni(2-SO2) was structurally characterized and has a unique side-on SO2 coordination mode with a Ni-S-O angle of 60.49(5)°. DFT calculations of (MesNHC2oXy)Ni(2-SO2) are consistent with a Ni(II) center and an activated SO2 fragment. DFT calculations also support an initial oxidative addition at either the S-F or S-C positions, which have similar energetics.