Carbon–Carbon Bond Activation by Main-Group Metal Complexes

Examples of carbon-carbon bond activation reactions at main-group metals (e.g. Mg, Al, Zn, Sn) are described in this review. Key approaches are discussed, and divergent reactivity compared to transition metal complexes highlighted. Several distinct mechanisms for C–C bond activation at main group metals have been proposed, with the key C–C bond activation step occurring by (i) beta-alkyl elimination, (ii) alpha-alkyl elimination, (iii) oxidative addition, or (iv) an electrocyclic reaction. Many of the known pathways involve an overall 2-electron redox process. Despite this, the direct oxidative addition of C–C bonds to main group metals is relatively rare, instead most reactions occur through initial installation of the main group site on a hydrocarbon scaffold (e.g. by a cycloaddition reaction or hydrometallation) followed by an -alkyl or -alkyl elimination step. Emerging applications of main group metal complexes as catalysts for the functionalisation of C–C bonds are also discussed.