Low-Coordinate Bismuth Cations

Chloride abstraction from the diamido-bismuth compound Bi­(Me2Si­{NAr}2)Cl (1, Ar = 2,6-i-Pr2C6H3) using MCl3 (M = Al, Ga) is a facile route to cationic species. Stoichiometric reactions afford the tetrachlorometallate salts [Bi­(Me2Si­{NAr}2)]­[MCl4] (2a, M = Al; 3a, M = Ga), whereas reaction with 0.5 equiv of the group 13 reagent gives the μ-chlorido bridged cations [{Bi­(Me2Si­{NAr}2)}2(μ-Cl)]­[MCl4] (2b, M = Al; 3b, M = Ga). The crystal structure of 2a shows a formally two-coordinate bismuth cation, with a Bi···Cl contact to the [AlCl4]− anion, whereas the structure of 3b shows a total of three Bi···Cl contacts to [GaCl4]−. Both species associate as {1:1}2 dimers in the solid state through additional Bi···Cl interactions. Attempted preparation of cationic complexes using either NaBR4 (R = Ph, Et) or [HNEt3]­[BPh4] were unsuccessful. Instead of forming the borate salts, the neutral compounds Bi­(Me2Si­{NAr}2)­R (4, R = Et; 5, R = Ph) were isolated as a result of aryl/alkyl transfer from boron to bismuth.