Activation of dinitrogen

The demand for ammonia for the manufacture of nitrogen-containing fertilizers and other chemicals is huge. Today s industrial manufacture of more than 100 billion tons of ammonia per year is achieved by the Haber and Bosch process, discovered more than 80 years ago. In this process a Fe-based heterogeneous catalyst is used. 

Very few organometallic complexes can model this reaction. A model catalytic reaction that is stoichiometric with respect to the proton (AH) and the electron donors has been reported. Such a reaction is of limited technological relevance in its current form, as production of each mole of ammonia would require 6 mol of AH and B.  

However, they may well be the guide for developing a reaction scheme that utilizes dihydrogen as the source for both protons and electrons. A few homogeneous catalytic reductions that are of relevance to biology, where dihydrogen acts as the source for both protons and electrons, are known (see Problem 7). 

---

A. Ozaki and K. Aika. Catalytic Activation of dinitrogen, ibid. pp. 87-158, Volume 7 B.E. Koel and G.A. Somorjai. Surface stmctural chemistiy, pp. 159-218. 

ELECTROCATALYTIC REDUCTION OF DINITROGEN AND NITROGEN OXIDES 9.10.6.1 Electrocatalytic Activation of Dinitrogen... 

Reactions other than Lewis acid-base associations/dissociations are frequently observed wit donor molecules, leading notably to solvolysis, oxygen or sulfur abstraction, insertion reaction and carbon-carbon coupling reactions. The tendency to form metal-element multiple bonds i remarkable in this respect the activation of dinitrogen by tantalum or niobium is unique. Th formation and chemistry of constrained reactive metallacycles open another promisin fast-developing area, on the frontier with organometallic chemistry. 

A. Ozaki, K. Aika Catalytic Activadon of Dinitrogen The third chapter is a comprehensive and critical review of studies on the catalytic activation of dinitrogen, including chemisorption and coordination of dinitrogen, kinetics and mechanism of ammonia synthesis, chemical and instrumental characterization of active catalysts, and homogeneous activation of dinitrogen including metal complexes (353 references). 

H. Heinemann History of Industrial Catalysis. -J. C. R. Turner An Introduction to the Theory of Catalytic Reactors. - A. Ozaki, KAika Catalytic Activation of Dinitrogen. - M. E. Z)ry The Fischer-Tropsch Synthesis. - J. H. Sinfelt Catalytic of Hydrocarbons. 

A. Ozaki, K. Aika Catalytic Activation of Dinitrogen, in R. H. Anderson, M. Boudart (eds.) Catalysis Science and Technology, vol. 1, Springer Verlag, Berlin-Heidelberg-New York 1981, pp. 87-158. 

Model complexes employed in extended Hilckel MO calculations on the activation of dinitrogen. 

Proposed activation of dinitrogen in the V -catecholateh and V -dicarboxylate systems.h l... 

In 1960 a group of microbial biochemists in the Central Research Laboratories of the Dupont de Nemours Chemical Corporation, USA, broke through a barrier that had impeded researchers for at least two decades. They extracted from a species of nitrogen-fixing bacteria a solution containing the enzyme which is responsible for the activation of dinitrogen." It was called nitrogenase, and, in appropriate conditions, it bound N2 from the atmosphere and reduced it to ammonia. 

The activation of dinitrogen for NH3 synthesis, oxidative fixation to nitric acid and fertilizers, organic amine and heterocyclic synthesis, and amino acid synthesis is a topic that has generated much interest. The sequence of filled molecular orbitals of the nitrogen is a-g, lcr , ... 

In 2004 and 2005 the photochemical activation of dinitrogen with transition metal model complexes of the Sellmann type nitrogenase was studied using CPMD [193, 194], A dinuclear complex — designed to emulate the open-side FeMoco model -was simulated. Several side reactions were observed which have to be suppressed in order to arrive at the reduced species [194]. Chelate effects and their partial dissociation as well as low temperatures led to successful events. An optimized design of the complexes to inhibit side reactions was suggested [194]. 

Fixation of carbon dioxide and formaldehyde in their intact form on a metal centre is a primary goal in metal-promoted transformations of a C molecule, provided it forms metal-carbon bonds. Formation of formaldehyde and carbon dioxide complexes is, however, a quite rare reaction, in spite of the various strategies applied so far. On the contrary, coordination of dinitrogen has been found in a number of complexes all the mononuclear compounds so far identified prefer the end-on bonding mode. Activation of dinitrogen, however, can be much more pronounced in ca.se N2 binds the metal in a side-on fashion. 

The activation of dinitrogen molecule is a process to break or weaken the N=N bond. There are three methods to be used to activate nitrogen molecule (1) Adsorbed activation of catalyst (2) Electron donation activation by using dinitrogen complex (3) Coordinated activation by biologic nitrogenase. 

Semproni SP, Chirik PJ. Activation of dinitrogen-derived hafnium nitrides for nucle-ophUic N-C bond formation with a terminal isocyanate. Angew Chem Int Ed. 2013 52 12965-12969. 

Evans WJ, Fang M, Zucchi G, et al. Isolation of dysprosium and yttrium complexes of a three-electron reduction product in the activation of dinitrogen, the (N2) radical. JAm Chem Soc. 2009 131 11195-11202. 

---