Flash Communication: Sulfonyl Fluoride Activation via S-F and C-S Bond Cleavage by a Ni(0) Bis-Bidentate ‑Heterocyclic Carbene Complex.

This work investigates possible mechanisms and intermediates in the reactivity of -toluenesulfonyl fluoride with a new bidentate -heterocyclic carbene (NHC) nickel complex, (NHC Xy)-Ni-(COD) (Mes = 2,4,6-trimethylphenyl, Xy = -xylyl, COD = cyclooctadiene). (NHC Xy)-Ni-(COD) was synthesized from the corresponding bis-(imidazolium) salt precursor, [NHC Xy]-[Br], and both were structurally characterized. (NHC Xy)-Ni-(COD) reacts with 1 equiv of -toluenesulfonyl fluoride to furnish (NHC Xy)-Ni-(η-SO), HF, and 1/2 equiv of 4,4'-dimethylbiphenyl. (NHC Xy)-Ni-(η-SO) was structurally characterized and has a unique side-on SO coordination mode with a Ni-S-O angle of 60.49(5)°. DFT calculations of (NHC Xy)-Ni-(η-SO) are consistent with a Ni-(II) center and an activated SO fragment. DFT calculations also support an initial oxidative addition at either the S-F or S-C position, which have similar energetics.