The development of cationic organopnictogen(V) compounds has witnessed increased attention in recent years, due to their powerful application as Lewis acids in catalysis. In particular, cationic fluorotriarylphosphonium complexes (e.g. [(C6F5)3PF]+[(C6F5)4B]-) have demonstrated their usefulness as Lewis acid catalysts for organic synthesis, finding applications in hydrodefluorination, hydrosilylation, Friedel-Crafts dimerization of 1,1-diphenylethylene, dehydrocoupling, and deoxygenation of ketones. Besides the rich chemistry of the fluorophosphonium cations, antimony and in particular examples of bismuth based halopnictonium analogs have been comparatively much less explored and only few examples exist in the literature. Herein, we represent the synthesis and characterization of a series of mono-, di- and trinuclear fluorotriarylbismuthonium cations bearing differently substituted aryl groups (Ar = xanthene, Ph, Mes and 3,5-tBu-C6H3), contributing to the expansion of the spectrum of haevier halopnictonium cations. These compounds were prepared by F-abstraction from the Bi(V)- triaryl difluoride parent compounds with NaBArF (BArF- = B[C6H3-3,5-(CF3)2]4-). Depending on the substitution, different structures could be obtained in the solid state. Trinuclear and binuclear complexes, are held together through one bridging fluoride (μ-F) between two Bi(V) centers. By further fine-tuning the ligand scaffold, the presence of Me groups in both ortho-positions of the aryl ring led to the isolation of the first mononuclear fluorotriarylbismuthonium cation that is not stabilized by the introduction of additional electronic effects. Structural parameters were obtained via single crystal X-ray diffraction (XRD) and their behavior in solution was studied by NMR spectroscopy.

Synthesis and structure of mono-, di- and trinuclear fluorotriarylbismuthonium cations

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