π-Coordinated arene metal complexes and catalysis

Metal complexes formed from π-coordination of aromatic groups to metal centres may undergo reactions at the coordinated arene that do not occur for the unbound arene. Upon completion of such reactions, the coordinated arene product can be liberated from the metal complex by thermal or photolytic methods. A catalytic approach can also be envisaged in which the arene transiently π-coordinates to the metal centre, reacts and then undergoes arene exchange for further starting arene. The significant challenge to this catalytic approach is to balance reactivity with arene exchange. In this review, we summarise the synthesis and reactivity of π-arene metal complexes. We go on to discuss the features of arene exchange and conclude with a comprehensive review of catalytic reactions proceeding via π-arene intermediates.