NMR studies on the reactivity of aluminium compounds with an unsaturated alcohol

Abstract

The interaction of an unsaturated alcohol, 10-undecen-1-ol (CH2 =CH(CH2)8CH2OH), with aluminium compounds AlEt3 and MAO (30% toluene solution) has been studied. The reactions were investigated at room and elevated temperatures and followed by 1H, 13C and 27Al NMR-spectroscopy. The alcohol end group of 10-undecen-1-ol reacts quantitatively with aluminium alkyls (AlEt3 as well as AlMe3 present in MAO), liberating alkane gas and forming in the first step the dimeric complexes [R'2AlOR]2 and [R'Al(OR)2]2 (R' = Me, Et; R = 10-undecen). In the presence of excess 10-undecen-1-ol the alkyl aluminium alkoxides are found to generate tetrameric aluminium compounds, Al4(R')(n)(OR)12-(n) (n = 6,4) containing six-coordinated central aluminium surrounded by six oxygen atoms. The structural assignment is based on 13C as well as 27Al NMR, where narrow resonances at 8.21 and 7.3 ppm are observed for Al4Me6(OR)6 and Al4Et6(OR)6, respectively. Besides the above reaction between the alcohol moiety and AIRs another effect was also visible in the reaction of 10-undecen-1-ol with MAO. Broad carbon resonances were observed in 13C NMR at the downfield side of the normal olefinic and alkoxy carbon resonances, indicating some kind of interaction of methylaluminoxane with the corresponding carbon atoms.