Salts of octabismuth(2+) polycations crystallized from Lewis-acidic ionic liquids

The reaction of Bi and BiCl3 with RbCl or CsCl in the Lewis-acidic ionic liquid (IL) [BMIm]Cl center dot 4AlCl(3) at T = 200 degrees C yielded air-sensitive, shiny black crystals. X-ray diffraction on single crystals revealed the hexagonal structures of two new salts (Bi-8)M[AlC4](3) (M = Rb, Cs), which are isostructural to the high-temperature form of (Bi-8)Tl[AlCl4](3). The known (Bi-8)(2+) polycation is a square antiprism and can be interpreted as an arachno cluster following modified Wade rules. The crystal structure is a complex variant of the hexagonal perovskite structure type ABX(3) with A = (Bi-8)(2+), B = M+ and X = [AlCl4] (-) Chiral strands infinity(1){M[AlCl4](3)}(2-) (M = Rb, Cs) run along [001]. The (Bi-8)(2+) polycations are only weakly coordinated inside a cage of 24 chloride ions and show dynamic rotational disorder at room temperature. Upon slow cooling to 170 K, the reorientation of the clusters was frozen, yet no long-range order was established.