The disproportionations and synproportionations of tbutylferrocenes and the ligand exchanges between the ferrocenes and benzene have been studied. The steric effects of the t-butyl groups were found to significantly affect the ratio of the products obtained. In these reactions, aluminium chloride attacks and abstracts the cyclopentadienyl ring. As a result, the ferrocene molecule decomposes into two fragments. The aluminium chloride selectively attacks the least sterically hindered cyclopentadienyl ring. The steric effect for a cyclopentadienyl ring bearing two t-butyl groups is substantial and inhibits attack by aluminium chloride. The product therefore contains the cyclopentadienyl ring which has the higher steric hindrance (i.e. the 1,3-di-substituted cyclopentadienyl ring).