Polydentate Amidinato‐Silylenes, ‐Germylenes and ‐Stannylenes

This review article focuses on amidinatotetrylenes that potentially can (or have already shown to) behave as bi‐ or tridentate ligands because they contain at least one amidinatotetrylene moiety (silylene, germylene or stannylene) and one (or more) additional coordinable fragment(s). Currently, they are being widely used as ligands in coordination chemistry, small molecule activation and catalysis. This review classifies those that have been isolated as transition metal‐free compounds into five families that differ in the position(s) of the donor group(s) (D) on the amidinatotetrylene moiety, namely: ED{R1NC(R2)NR1}, EX{DNC(R2)NR1}, EX{R1NC(D)NR1}, EX{DNC(R2)ND} and E{R1NC(R2)ND}2 (E=Si, Ge or Sn). Those that do not exist as transition metal‐free compounds but have been observed as ligands in transition metal complexes are cyclometallated and ring‐opened amidinatotetrylene ligands. This article presents schematic descriptions of their structures, the approaches used for their syntheses and a quick overview of their involvement (as ligands) in transition metal‐catalysed reactions. The literature is covered up to the end of 2023. This review article classifies the title compounds into families that differ in the position(s) of the donor group(s) D on the corresponding amidinatotetrylene moiety (E=Si, Ge, Sn), schematically presents the structures of the members of each family, and describes the synthetic approaches utilized for their preparation and their use as ligands in transition metal‐catalysed reactions.