AbstractThe reagent 4‐(pentafluorosulfanyl)benzenediazonium tetrafluoroborate (1) was synthesized and isolated as a stable salt for the first time; its application in a wide assortment of transformations was subsequently investigated. A series of novel SF5‐bearing alkenes, alkynes, and biaryl derivatives were synthesized by employing Heck–Matsuda, Sonogashira, and Suzuki coupling protocols. Dediazoniation with TMSX (X = Hal; N3; and CN) and NH4SCN in [BMIM][BF4] as solvent furnished the corresponding p‐SF5–C6H4X derivatives. The azide derivative p‐SF5–C6H4N3 entered into click chemistry with phenylacetylenes to furnish the corresponding triazoles. The 4,4′‐bis(pentafluorosulfanyl)biphenyl was synthesized by homo‐coupling using Pd(OAc)2. The corresponding azo compounds were obtained through azo‐coupling with reactive aromatic nucleophiles (1,3‐dimethoxybenzene, 1,3,5‐trimethoxybenzene, 1,2,4‐trimethoxybenzene, aniline and phenol). Fluorodediazoniation in [BMIM][PF6] and [BMIM][BF4] selectively furnished the fluoro derivative p‐SF5–C6H4F. Dediazoniation in [BMIM][NTf2] gave p‐SF5–C6H4OS(O)(CF3)=NSO2CF3 as the major and p‐SF5–C6H4‐NTf2 as the minor products. Homolytic dediazoniation in MeCN/NaI gave the unsymmetrical biaryls p‐SF5–C6H4‐Ar (ArH = mesitylene and p‐xylene) along with p‐SF5–C6H4I. Analysis of the dediazoniation product mixtures indicated that dediazoniation of p‐SF5–C6H4N2+ BF4– in low nucleophilicity, highly ionizing, solvents (TfOH, TFE, HFIP, TFAH) is mainly heterolytic, while in MeOH it is mainly homolytic. The isodesmic reaction p‐SF5–C6H4+ + R‐C6H5 → SF5–C6H5 + p‐R‐C6H4+ (with R = NO2, CF3, H) was gauged by DFT at various levels and by PCM.