LAUSR

This review article describes the chemistry of transition-metal complexes containing heavier group 14 elements (Si, Ge, and Sn) as the σ-electron-acceptor (Z-type) ligands and discusses the characteristics of bonds between the transition metal and Z-type ligand. Moreover, we review the iridium hydride mediated cleavage of E-X bonds (E=Si, Ge; X=F, Cl), where the key intermediates are pentacoordinate silicon or germanium compounds bearing a dative M→E bond.