Terminal Iron Dinitrogen and Iron Imide Complexes Supported by a Tris(phosphino)borane Ligand

Adaptable metallaboratranes: A tris- (phosphino)borane ligand stabilizes both low-valent FeN2 complexes and a mid-valent imido species with a FeNAr bond, thanks to its ability to shuttle between trigonal-bipyramidal and pseudotetrahedral geometries by elongation of the apical iron–boron bond (see picture).