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.
Assigning Hapticity to Cyclopentadienyl Derivatives of Antimony and Bismuth
摘要:
The chelating diamide [Me2Si{NAr}(2)](2-) (Ar = 2,6-i-Pr2C6H3) has been used as an ancillary ligand in antimony and bismuth chemistry. In contrast to the monomeric antimony chloride compound Sb(Me2Si{NAr}(2)) Cl (1a), the bismuth derivative (1b) exists as a trimer in the solid state, linked by Bi center dot center dot center dot(arene) pi-bonding and Bi center dot center dot center dot Cl interactions. Compounds 1a,b are used as an entry point into rare antimony and bismuth compounds incorporating Cp and Cp* ligands. Reactions of the chlorides with LiCp and KCp* afford the organometallic species E(Me2Si{NAr}(2))-(C5R5) (2a, R = H, E = Sb; 2b, R = H, E = Bi; 3a, R = Me, E = Sb; 3b, R = Me, E = Bi). Variable-temperature NMR experiments indicate different fluxional processes occur in solution involving facile haptotropic shifts of the [C5R5](-) ring. Structural characterization of 2b and 3a,b reveals monomeric compounds in which the cyclopentadienyl-derived ligand adopts a low hapticity in the solid state.