Transition metal complexes with asymmetric tridentate peripheral organosilyl ligands: their impact in homogeneous catalysis

Silyl-based tridentate ligands [SiL 2 ] n− (n = 1, 2; L = PR 3 , NR 2 or other groups) have emerged over the last decades as a versatile class of ligands for transition metal (TM) chemistry. TM–(κ 3 - Si , L 2 ) complexes display unique structural features and reactivity that arise directly from the incorporation of a strongly σ-donating silyl group into the pincer ligand framework. While most studies have focused on systems where silicon occupies the central position of the tridentate scaffold, recent efforts have shifted toward the development of TM complexes in which the silicon atom is located at the periphery of the ligand. This alternative design opens unexplored opportunities to fine-tune electronic and steric properties, offering fresh perspectives for catalyst optimization and the discovery of unprecedented reactivity patterns. This review summarizes and discusses the most recent advances in this emerging area, highlighting strategies for incorporating peripheral silicon into the skeleton of the ligand and exploring its impact on the coordination chemistry, reactivity and catalytic activity of the resulting TM complexes.