Coordination of Lewis Acids to Transition Metals: Z-Type Ligands

This chapter provides a comprehensive review of M -> Z complexes, that is to say complexes featuring Lewis acids coordinated as sigma-acceptor ligands. The preparation, structure and bonding, as well as the characteristic features of M -> Z complexes are discussed. Only Lewis acids derived from the p-block elements are considered, with a focus on two-center M -> Z interactions supported by donor sidearms. The chapter is organized according to (1) the nature of the Lewis acid moiety (based on group 13, 14, 15 or 16 elements), (2) the way the M -> Z interaction is formed (by B-H activation of pro-ligands or direct coordination of preformed ambiphilic ligands) and (3) the type of complexes (M -> interactions supported by 3, 2 or 1 donor sidearms, unsupported M -> Z interactions).