Carbon-fluorine bond cleavage in fluoroarenes via a niobium(iii) imido complex: From stoichiometric to catalytic hydrodefluorination

The mechanism of activation of C-F bonds in fluoroarenes using a well-defined niobium(iii) imido complex has been investigated. The Nb(iii) arene species [BDI]Nb(N^tBu)(η⁶-C₆H₆), 1, (BDI = β-diketimate), reacts stoichiometrically with fluoroarenes to yield niobium(v) aryl fluorides. Spectroscopic analysis supported by DFT calculations revealed the critical involvement of a Nb(iii) fluoroarene-bound species. In contrast to previous reports of related reactivity, we found that perfluorinated arenes (i.e. those normally assumed to bear more 'activated' C-F bonds) are, in the present system, much less reactive towards C-F bond cleavage than mono- or difluoro-substituted arenes. In addition to demonstrating stoichiometric hydrodefluorination reactions, we also describe an efficient and mild hydrodefluorination of mono- and di-fluoroarenes that is catalytic in niobium. This journal is