Catalytic C–H to C–M (M = Al, Mg) bond transformations with heterometallic complexes
C–H functionalisation is one of the cornerstones of modern catalysis and remains a topic of contemporary interest due its high efficiency and atom-economy. Among these reactions, C–H borylation, that is the transformation of C–H to C–B bonds, has experienced a fast development because of the wide utility of organoboron reagents as synthetic intermediates. The mechanistic background is now well-understood and the role of transition metal boryl or σ-borane intermediates in this transformation is well documented. This mini-review focuses on efforts made by our group, and others, to establish palladium- and calcium-catalysed methods for C–H metalation employing heavier main group elements (M = Al, Mg). These are new catalytic reactions first accomplished in our group that we have termed C–H alumination and magnesiation respectively. Unusual heterometallic complexes have been identified as key on-cycle intermediates and their unique reactivity is discussed in the context of new catalytic pathways for C–H functionalisation. Hence, this mini-review summarises the recent progress in the area of C–H metalation reactions as well as the new opportunities that may arise from this concept.