The discussion is split into three distinct approaches, namely -alkyl migration, oxidative addition, and those initiated by cycloaddition reactions. Much of the early mechanistic work on -alkyl migration was performed with group 4 metallocene complexes as part of understanding polymerization catalysis . Through discussion of mechanism, we aim to highlight the divergent chemistry shown by main-group metal complexes compared to their transition metal counterparts and touch on the potential implications in synthesis The reversible stoichiometric formation of iso-butene gas and trimethylaluminium was observed via sp 3 C-C -bond activation, presumed to occur through a -methyl migration reaction (Scheme 2). The release of three equivalents of iso-butene gas provides an entropic driving force for the forward reaction.