Synthesis and crystal structures of Cd[AlCl4]2 and Cd2[AlCl4]2

Colorless single crystals of Cd[AlCl4]2 grow from the melt of CdCl2 and AlCl3 upon slow cooling from 250°C. The crystal structure [monoclinic, P1a1, Z = 2, a = 1288.7(2), b = 660.2(1), c = 705.1(1) pm, β = 92.89(1)º] may be derived from hexagonally closest packed layers of Cl−. Octahedral and tetrahedral holes are filled with Cd2+ and Al3+ in a 1:2 ratio between all layers stacked in the [104] direction. Cd[GaCl4]2 and Cd[AlBr4]2 are isotypic. Reduction of Cd[AlCl4]2 with excess cadmium shot and slow cooling from 350°C yields plate‐like very moisture‐sensitive, colorless single crystals of Cd2[AlCl4]2. The crystal structure [triclinic, C1, Z = 2, a = 655.47(3), b = 1135.26(1), c = 935.23(6) pm, α = 89.70(2)º, β = 103.61(1)º, γ = 90.455(1)º] is built from slabs stacked in the [100] direction consisting of ethane‐like [Cd2Cl6] units with a CdCd distance of 256.1 pm sharing common vertices with [AlCl4] tetrahedra.