Matrix isolation and ab initio study of the reactions of (CH3)(3)Al with CH3OH and H2O: spectroscopic evidence for (CH3)(2)AlOCH3

The matrix isolation technique has been used to investigate the initial pro ducts of the room and high temperature reaction of trimethylaluminum with m ethanol and its isotopomers, as well as water, in a flowing reactor system. Reaction went substantially to completion as indicated by a dramatic reduc tion of bands due to parent (CH3)(3)Al when dilute samples of Ar/CH3OH were added to the flowing gas mixture, and vice versa. Ar least two products we re formed, an initial intermediate that has been identified as (CH3)(2)AlOC H3, and one or more oligomers of this species (i.e. dimers and/or trimers). Heating the reaction zone above 200 degrees C following by matrix trapping led to complete destruction of the bands due to (CH3)(2)AlOCH3, and an inc rease in the bands due to the oligomers. The production of CH3D as was also noted with CD3OD was employed, bur not when CD3OH was used. Ab initio calc ulations at the RHF/6-31G* and B3LYP/6-31G* levels were carried out on (CH3 )(2)AlOCH3; these calculations support the identification of this species. Similar experiments involving (CH3)(3)Al and H2O did not lead to any new pr oduct bands, although reaction apparently occurred in the reaction zone, as evidenced the growth of strong bands due to CH4. (C) 1999 Elsevier Science B.V. All rights reserved.