The Lewis acid-base adducts of bismuth and aluminium trihalides — crystal structures of [Bi2X4][AlX4]2(X = Cl, Br)

Abstract

AbstractThe reactions of BiCl3with AlCl3and of BiBr3with AlBr3yield [Bi2Cl4][AlCl4]21and [Bi2Br4][AlBr4]22in almost quantitative yield. The reactions were performed in closed, evacuated glass ampoules at temperatures of 240 °C and 200 °C, respectively. The colorless and yellow crystals are sensitive towards hydrolysis by moist air.1crystallizes in the monocline space groupP21/c(a= 7.7322(2) Å,b= 11.9565(3) Å,c= 10.3535(3) Å,β= 95.090(2)°,Z= 2),2crystallizes in the triclinic space groupP-1 (a= 7.693(2) Å,b= 7.706(2) Å,c= 9.739(2) Å,α= 104.19(2)°,β= 102.65(2)°,γ= 99.46(2)°,Z= 1). Both structures are made up of [Bi2X4] cations and [AlX4]–anions. The centrosymmetric cations consist of four membered Bi2X2rings with an additional halogen atom attached to each Bi atom in atransarrangement. The tetrahalogeno aluminate ions are almost regular tetrahedral. Although both compounds contain isomorphous ions, the structures of1and2are not isotypic. The different packing can be understood by abstracting both structures to simple AB2types.1adopts the PtHg2structure type with eightfold coordination of the cations whereas2adopts the MoSi2structure with tenfold coordination.