Controlled Mono- and Double-Insertion of Sulfonamide Fragments into Ni–S Bonds of Nickel(II) Dithiocarbamate Complexes via Sulfonyl Azide Reactivity

A novel approach for controlled mono- and double-insertion of sulfonamide fragments into Ni-S bonds of [Ni(S₂CNR₂)₂] complexes has been developed using aryl and alkyl sulfonyl azides as sulfonamide sources. The reaction selectivity is governed by the choice of solvent (hexafluoro-2-propanol for the monoinsertion versus isopropanol for the double-insertion) and temperature (50 and 80 °C, respectively). This method provides convenient access to previously unreported monoinsertion products [NiL(S₂CNR₂)] along with the double-insertion complexes [NiL₂] (L = NSO₂(R')S₂NR₂) under mild conditions. The scope of the reaction was demonstrated using 18 sulfonyl azides and 6 nickel(II) dithiocarbamates, affording the target complexes (38 examples) isolated in 9-97% yields. The method's practicality was confirmed through gram-scale syntheses of three representative examples (72, 76, and 92%). X-ray diffraction analysis of 15 new complexes revealed that sulfonamide fragments occupy axial positions relative to the dithiocarbamate plane, with the modified C-S bonds showing inequivalent lengths (1.76-1.78 Å for C-SN vs ∼ 1.71 Å for C-SNi). Mechanistic studies uncovered that insertion products can undergo spontaneous disproportionation in solution.