Aluminum cluster anions were reacted with methyl iodide vapor in a fast-flow tube apparatus, yielding primarily I and clusters of the type AlnI-. Based on thermodynamic considerations, the presence of F is taken to indicate a neutralization reaction pathway whereby clusters of the type AlnCH3 are formed. Comparison of relative reaction rates to previously measured electron affinities suggests that the Al-n-CH3 interaction is covalent, rather than ionic, in nature. It is suggested that the neutral cluster complexes reported here may hold potential as high energy fuel dopants. (C) 2003 Elsevier Science B.V. All rights reserved.