Structural Aspects of Chlorine‐Aluminium Alkoxides

LiAlH 4 and AlCl 3 reacted in a ratio 1:3 to obtain Cl 2 AlH, which is stabilised by the addition of two equivalents of N‐methylpiperidine (nmp) to form dichloroalane ( 1 ) as bis adduct of nmp. Compound 1 was allowed to react with 2,6‐ t Bu‐4‐MeC 6 H 2 OH and HO c Hex in a 1:1 ratio to get compounds 2 and 3 , respectively. Cl 2 Al(2,6‐ t Bu‐4‐MeC 6 H 2 O)(nmp) ( 2 ) is a monomer in which the central aluminium atom is tetracoordinate. Contrary to the parent compound 1 , compound 2 is stabilised by only one nmp molecule. The larger bulk of the alkoxide in 2 prevents the second nmp molecule to reach the aluminium atom. Compound 3 crystallises as unique anionic tri‐nuclear aluminium entity [Al 3 Cl 6 (O R ) 4 ] – [nmp 2 H] + with a protonated nmp as countercation. The lesser bulk of the cyclohexanolate leads to a higher oligomerisation of R OAlCl 2 ( R = cyclohexyl). When a relatively bulkier alcohol, 1‐methylcyclohexanol, was allowed to react with mixtures of LiAlH 4 and AlCl 3 prepared in 1:1 and 1:3 ratios in solution, compounds 4 and 5 , respectively, were obtained. Both compounds ((HClAlO R ) 2 ( 4 ) and (Cl 2 AlO R ) 2 ( 5 ), R = c HexMe‐1)) are dimers with oxygen as bridging atom in the Al 2 O 2 rings. All compounds 2 , 3 , 4 , and 5 were structurally characterised by X‐ray diffraction on single crystals.