Because dinitrogen is an inert mol., to activate and transform it into higher value organo-nitrogen compds. remains a challenge for synthetic chemists. It is known that transition metal complexes bind N2 if the appropriate ligand architecture is utilized. The new o-phenylene-bridged NPN ligands presented here have demonstrated this ability with zirconium, binding dinitrogen in a bridging, side-on fashion to form strongly activated bimetallic complexes. Small variations in the ligand structure, esp. substituents in the ortho position of the N-aryl group can have a dramatic effect on the reactivity of the metal center. The synthesis and reactivity of these zirconium dinitrogen complexes will be discussed. The activation of dinitrogen under mild conditions is desirable. Previous work with similar NPN ligands have formed strongly bound side-on end-on tantalum dinitrogen complexes at ambient conditions from the precursor metal hydrides and attempts at replicating this behavior with the new o-phenylene-bridged NPN ligand is discussed. [on SciFinder(R)]