Lewis Acidity of Si6Cl12 and Its Role as Convenient SiCl2 Source

The free cyclohexasilane Si6Cl12 (1) was obtained in 66% yield from the corresponding Cl– diadduct [nBu4N]2[1·2Cl] and AlCl3 in C6H6. The substituted cyclohexasilane 1,1-(Cl3Si)2Si6Cl10 (2), however, cannot be liberated from [nBu4N]2[2·2Cl] under comparable reaction conditions. Instead, a mixture of several products was obtained, from which the oligosilane Si19Cl36 (3) crystallized in low yields. X-ray crystallography revealed 3 to consist of two Si5 rings, bridged by one silicon atom. Compound 1 possesses Lewis acidic sites above and below the ring centroid. Competition experiments reveal that their corresponding acid strengths are comparable to that of BCl3. The reaction of 1 with 6 equiv of 1,3-bis­(2,6-diisopropylphenyl)­imidazol-2-ylidene (Idipp) leads to a complete breakdown of the cyclic scaffold and furnishes the dichlorosilylene adduct Idipp–SiCl2.