Dinitrogen activation by group 4 and group 5 metal complexes supported by phosphine-amido containing ligand manifolds

This review surveys the iterative approaches to ligand design for groups 4 and 5 transition metal complexes relevant to nitrogen fixation made by the Fryzuk group over the last 25 years. The coordination chemistry of multidentate ligands that incorporate phosphine and amido donors with zirconium, titanium, tantalum and niobium, and their ability to bind and functionalize molecular nitrogen is surveyed. In this review, the sequential design of these ligand sets is documented with the ultimate, as yet unrealized goal to discover a homogeneous system that can use dinitrogen as a feedstock and convert it to higher value organo-nitrogen materials in a catalytic process.