Structural aspects of chlorine-aluminium alkoxides 

Abstract LiAlH4and AlCl3reacted in a ratio 1:3 to obtain Cl2AlH, which is stabilised by the addition of two equivalents of N-methylpiperidine (nmp) to form dichloroalane (1) as bis adduct of nmp. Compound1was allowed to react with 2,6-tBu-4-MeC6H2OH and HOcHex in a 1:1 ratio to get compounds2and3, respectively. Cl2Al(2,6-tBu-4-MeC6H2O)(nmp) (2) is a monomer in which the central aluminium atom is tetracoordinate. Contrary to the parent compound1, compound2is stabilised by only one nmp molecule. The larger bulk of the alkoxide in2prevents the second nmp molecule to reach the aluminium atom. Compound3crystallises as unique anionic tri-nuclear aluminium entity [Al3Cl6(OR)4]–[nmp2H]+with a protonated nmp as countercation. The lesser bulk of the cyclohexanolate leads to a higher oligomerisation ofROAlCl2(R= cyclohexyl). When a relatively bulkier alcohol, 1-methylcyclohexanol, was allowed to react with mixtures of LiAlH4and AlCl3prepared in 1:1 and 1:3 ratios in solution, compounds4and5, respectively, were obtained. Both compounds ((HClAlOR)2(4) and (Cl2AlOR)2(5),R=cHexMe-1)) are dimers with oxygen as bridging atom in the Al2O2rings. All compounds2,3,4, and5were structurally characterised by X-ray diffraction on single crystals.