text: The ability of Lewis acids to coordinate to transition metals as σ-acceptor ligands was recognized as early as in the 1970s, but the so-called Z-type ligands remained curiosities until the early 2000s. Over the last decade, significant progress has been made in this area, especially via the incorporation of Lewis acid moieties into multidentate, ambiphilic ligands. The understanding of the nature and influence of metal→Z-ligand interactions has considerably improved and the scope of Lewis acids susceptible to behave as σ-acceptor ligands has been significantly extended.