Dinitrogen‐Transition Metal Complexes: Synthesis, Properties, and Significance

Compared to the large number of CO complexes, N 2 complexes are still rare. In certain cases they may be formed from N 2 gas and metal compounds under physiological conditions, and are therefore frequently considered as possible intermediates in N 2 assimilation. However, despite numerous attempts it has not yet been possible to reduce the N 2 ligand of a fully characterized N 2 complex to NH 3 . This negative evidence recently prompted the discoverers of the first dinitrogen complex, the [Ru(NH 3 ) 5 N 2 ] 2⊕ ion isolated in 1965, to express doubt whether such complexes really do play a part in the enzymatic reduction of N 2 . The latest findings nevertheless incline toward a somewhat more optimistic view. Thus, the mild partial reduction of the N 2 ligand in metal complexes with inert gas configuration, hitherto considered nonreducible, justifies the hope that a suitable system permitting the catalytic reduction of molecular nitrogen under normal conditions will one day be found. Even apart from any technical potential, the N 2 complexes constitute an interesting chapter of modern inorganic chemistry.