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 mu-chlorido bridged cations [{Bi(Me2Si{NAr}(2))}(2)(mu-Cl)][MCl4] (2b, M = Al; 3b, M = Ga). The crystal structure of 2a shows a formally two-coordinate bismuth cation, with a Bi center dot center dot center dot Cl contact to the [AlCl4](-) anion, whereas the structure of 3b shows a total of three Bi center dot center dot center dot Cl contacts to [GaCl4](-). Both species associate as {1:1}(2) dimers in the solid state through additional Bi center dot center dot center dot Cl interactions. Attempted preparation of cationic complexes using either NaBR4 (R = Ph, Et) or [HNEt3] [BPh4] compounds Bi(Me2Si{NAr}(2))R (4, R = Et; 5, R = Ph) were is were unsuccessful. Instead of forming the borate salts, the neutral isolated as a result of aryl/alkyl transfer from boron to bismuth.