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Nitrogen fixation is the process by which nitrogen is taken from its relatively inert molecular form (N2) in the atmosphere and converted into nitrogen compounds useful for other chemical processes (such as, notably, ammonia, nitrate and nitrogen dioxide) •. Nitrogen fixation is performed naturally by a number of different prokaryotes, including bacteria, and actinobacteria certain types of anaerobic bacteria. Microorganisms that fix nitrogen are called diazotrophs. Some higher plants, and some animals (termites), have formed associations with diazotrophs. Biological nitrogen fixation was discovered by the Dutch microbiologist Martinus Beijerinck.
Biological Nitrogen Fixation Leguminous nitrogen-fixing plants The best-known are legumes (such as clover, beans, alfalfa and peanuts) which contain symbiotic bacteria called rhizobia within nodules in their root systems, producing nitrogen compounds that help the plant to grow and compete with other plants. When the plant dies, the nitrogen helps to fertilize the soil • . The great majority of legumes have this association, but a few genera (e.g., Styphnolobium) do not. Non-leguminous nitrogen fixing plants Plants from many other families have similar associations, including: Chemical nitrogen fixation Nitrogen can also be artificially fixed for use in fertilizer, explosives, or in other products. The most popular method is by the Haber process. This artificial fertilizer production has achieved such scale that it is now the largest source of fixed nitrogen in the Earth's ecosystem. The Haber process requires high pressures and very high temperatures and active research is committed to the development of catalyst systems that convert nitrogen to ammonia at ambient temperatures. The first dinitrogen complex was discovered in 1965 based on ammonia coordinated to ruthenium (Ru(NH3)5(N2)2+) This discovery was followed by the first example of homolytic cleavage of nitrogen by a molybdenum complex to two equivalents of a triple bonded MoN complex (1995). The first catalytic system converting nitrogen to ammonia at room temperature and 1 atmosphere was discovered in 2003 and is based on another molybdemum catalyst, a proton source and a strong reducing agent . See also | ||||||||
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