The use of crown ethers to access new M[Al2R6X] species. Synthesis and crystal structure of [K · dibenzo-18-crown-6] [Al2Me6Cl] · 2 C6H6

Potassium chloride does not react with trimethylaluminium in benzene in the absence of a crown ether. With the addition of dibenzo-18-crown-6, a normal liquid clathrate ensues. The composition of the parent compound has been established by a single crystal X-ray diffraction study. The space group is monoclinicP2₁/c with unit cell dimensionsa=21.319(8),b=9.512(4),c=21.081(8) Å, β=93.79(3)°, andρ _calc1.15 g cm^?3 forZ=4. Refinement led to a final conventionalR value of 0.049 for 2224 observed reflections. The anion has the expected angular geometry (Al?Cl?Al=120.0(1)°). There are two different types of benzene in the crystalline solid. One is associated with the K⁺ ion, while the other exists in layers normal to thea axis.