Chapter 11: Nitrogen Fixation

Synthetic ammonia production using nitrogen gas in the atmosphere and hydrogen gas derived from fossil fuels has been the most important, as well as the most primary energy-consuming, process in the modern chemical industry. However, organisms have fixed nitrogen gas to obtain nitrogenous biogenic substances essential for life at ambient conditions for billions of years. Since the mid-20th century, a great number of investigations have been carried out for the development of stoichiometric conversions of dinitrogen into ammonia or other nitrogen-containing compounds at ambient temperatures and pressures by using molecular transition metal complex compounds. Especially in recent years, remarkable progress has been made in the use of molecular complex catalysts in the reduction of dinitrogen to obtain ammonia, hydrazine, silylamines, or other nitrogen-containing compounds at ambient temperatures and pressures. Turnover frequencies for the catalytic formation of ammonia have now surpassed enzymic activities of biological nitrogen fixation.