Recent advances in transition metal catalysis featuring Z-type ligands

Abstract

Z-type ligands, characterized as σ-acceptors enhancing transition metal Lewis acidity, have recently emerged as powerful tools in transition metal catalysis. Although early studies were hampered by concerns over their instability and synthetic inaccessibility, subsequent design strategies involving rigid chelating frameworks and intramolecularly stabilized p-block elements (B, Al, Ga, Sb) have overcome these challenges, thereby revitalizing interest in Z-type ligand chemistry. These ligands stabilize intermediates, lower activation barriers, and enable new catalytic pathways. Notably, Z-type ligands enhance π-acid catalysis by increasing metal electrophilicity, thereby facilitating cyclization and hydroamination reactions. They have also proven effective in selective hydrogenations and in activating otherwise unreactive bonds, including E–F (E = Si, Ge, Sn) and acyl chlorides. The development of chiral Z-type ligands based on heavier elements (Sb, Bi) has further advanced asymmetric catalysis. Computational studies have further clarified how these ligands modulate the electronic properties of the metal center, influencing both reactivity and selectivity. This review summarizes recent progress in the development and application of Z-type ligands, highlighting their growing impact on modern synthetic chemistry.