Tetrelanes versus Tetrylenes as Precursors to Transition Metal Complexes Featuring Tridentate PEP Tetryl Ligands (E=Si, Ge, Sn)

Two synthetic approaches have until now been used to synthesize transition metal complexes having a tridentate (pincer or tripod) PEP tetryl (E=Si, Ge, Sn) ligand. These approaches differ in the metal-free precursor, tetrelane or tetrylene, that gives rise to the corresponding PEP tetryl ligand. Tetrelanes (PSiP silanes, PGeP germanes and PSnP stannanes and simple phosphane-free stannanes) have led to tetryl ligands by oxidatively adding an E-X bond (X=H, C or halogen in most cases) to the metal atom of a low-valent transition metal complex, whereas tetrylenes (PGeP germylenes and PSnP stannylenes) have led to tetryl ligands upon insertion of their E atom into an M-X bond (X=Cl in most cases) of the metal precursor or through a derivatization of the E atom after the tetrylene fragment is coordinated to the metal. For each synthetic approach, all the currently known types of PEP tetryl ligand frameworks that have been found in transition metal complexes are presented and discussed in this review.

Automated summary

Two synthetic approaches have been utilized to synthesize transition metal complexes with tridentate PEP tetryl ligands. One approach involves the oxidative addition of an E-X bond (X=H, C or halogen) to a low-valent transition metal complex using tetrelanes as the metal-free precursor, while the other approach involves the insertion of an E atom into an M-X bond (X=Cl) of the metal precursor or derivatization of the E atom after coordination to the metal using tetrylenes. This review discusses the different types of PEP tetryl ligand frameworks found in transition metal complexes for each synthetic approach.