Bismuth Cations: Fluoride Ion Abstraction, Isocyanide Coordination, and Impact of Steric Bulk on Lewis Acidity

The molecular compound [BiDipp(2)(SbF6)], containing the bulky, donor-free bismuth cation [BiDipp(2)](+) has been synthesized and fully characterized (Dipp=2,6-iPr(2)-C6H3). Using its methyl analog [BiMe2(SbF6)] as a second reference point, the impact of steric bulk on bismuth-based Lewis acidity was investigated in a combined experimental (Gutmann-Beckett and modified Gutmann-Beckett methods) and theoretical approach (DFT calculations). Reactivity studies of the bismuth cations towards [PF6](-) and neutral Lewis bases such as isocyanides C equivalent to NR' revealed facile fluoride ion abstraction and straightforward Lewis pair formation, respectively. The first examples of compounds featuring bismuth-bound isocyanides have been isolated and fully characterized.