Tantalum

This review on coordination chemistry of tantalum covers the literature between 2003 and 2018. Tantalum complexes with ligands based on groups 15 (nitrogen, phosphorus, arsenic), 16 (oxygen, sulfur, selenium, tellurium), and 17 (fluorine, chlorine, bromine) as well as with mixed-donor ligands are the focus. Coverage of organometallic complexes is selective to give readers a more comprehensive understanding of the coordination chemistry of tantalum. Complexes with hydride and boron- and carbon-based ligands, including alkylidene, η2-allyl, allene, vinyl, alkene, alkylidyne, η3-allyl, alkyne, N-heterocyclic carbene (NHC), and CCC pincer ligands, are discussed. Complexes with alkyl, cyclopentadienyl, acyl, iminoacyl, and related ligands are generally not discussed. Tantalum is among the largest early transition elements and can easily form complexes with high coordination numbers, although six is the most common. In addition, the larger radii of tantalum ions lead to less tight coordination sphere and frequently observed stereodynamic properties of the complexes. Tantalum complexes have been used as precursors to make electronic materials through processes such as chemical vapor deposition or atomic layer deposition.