تثبيت النيتروجين: الفرق بين النسختين

[[قنبية|Cannabaceae]]: ''[[Trema (genus)|Tremaتريمة]]''

Artificial fertilizer production is now the largest source of human-produced fixed nitrogen in the [[الأرض|Earth]]'s [[نظام بيئي|ecosystem]]. Ammonia is a required precursor to [[سماد|fertilizers]], [[explosiveمتفجرات]]s, and other products. The most common method is the [[عملية هابر-بوش|Haber process]]. The Haber process requires high pressures (around 200 atm) and high temperatures (at least 400&nbsp;°C), routine conditions for industrial catalysis. This highly efficient process uses natural gas as a hydrogen source and air as a nitrogen source.<ref>http://www.epa.gov/watertrain/nitroabstr.html US Enivronmental Protection Agency: Human Alteration of the Global Nitrogen Cycle: Causes and Consequences by Peter M. Vitousek, Chair, John Aber, Robert W. Howarth, Gene E. Likens, Pamela A. Matson, David W. Schindler, William H. Schlesinger, and G. David Tilman</ref>

Much research has been conducted on the discovery of catalysts for nitrogen fixation, often with the goal of reducing the energy required for this conversion. However, such research has thus far failed to even approach the efficiency and ease of the Haber process. Many compounds react with atmospheric nitrogen to give [[dinitrogen complex]]es. The first dinitrogen [[Complexمعقد (chemistry)|complexتناسقي]] to be reported was based on [[روثينيوم|ruthenium]],[Ru(NH₃)₅(N₂)]²⁺.<ref>{{cite journal

Few compounds will cleave the N₂ molecule. Under an atmosphere of nitrogen, lithium metal converts to [[نتريد الليثيوم|lithium nitride]]. Treatment of the resulting nitride gives ammonia. Another example of [[تكسر متماثل|homolytic cleavage]] of dinitrogen under mild conditions was published in 1995. Two equivalents of a [[موليبدنوم|molybdenum]] complex reacted with one equivalent of dinitrogen, creating a [[رابطة ثلاثية]]ed MoN complex.<ref>"Dinitrogen Cleavage by a Three-Coordinate Molybdenum(III) Complex" Catalina E. Laplaza and Christopher C. Cummins ''Science'' 12 May 1995: 861–863.[[معرف الوثيقة الرقمي|10.1126/science.268.5212.861]]</ref> Since then, this triple bonded complex has been used to make [[nitrilesنتريل]].<ref>"A Cycle for Organic Nitrile Synthesis via Dinitrogen Cleavage" John J. Curley, Emma L. Sceats, and Christopher C. Cummins ''J. Am. Chem. Soc.'', 2006, 128 (43), pp. 14036–14037 {{DOI|10.1021/ja066090a}}</ref>

[[Trimethylsilyl chloride]], lithium, and nitrogen molecule react to give [[tris(trimethylsilyl)amine]], under catalysis by [[nichrome]] wire or [[chromiumكلوريد trichlorideالكروم الثلاثي]] in tetrahydrofuran.

Catalytic systems for converting nitrogen to ammonia have been developed since the 1980s.<ref>C. J. Pickett, "The Chatt Cycle and the Mechanism of Enzymic Reduction of Molecular Nitrogen", ''J. Biol. Inorg. Chem.'' 1996 1, 601–606.</ref> In 2003 another was reported based on molybdenum compound, a proton source, and a strong [[مختزل|reducing agent]].<ref>''Synthesis and Reactions of Molybdenum Triamidoamine Complexes Containing Hexaisopropylterphenyl Substituents'' Dmitry V. Yandulov, [[ريتشارد شروك|Richard R. Schrock]], Arnold L. Rheingold, Christopher Ceccarelli, and William M. Davis Inorg. Chem.; '''2003'''; 42(3) pp 796–813; (Article) {{DOI|10.1021/ic020505l}}</ref><ref>"Catalytic Reduction of Dinitrogen to Ammonia at a Single Molybdenum Center" Dmitry V. Yandulov and Richard R. Schrock ''[[ساينس|Science]]'' 4 July '''2003''': Vol. 301. no. 5629, pp. 76–78 {{DOI|10.1126/science.1085326}}</ref><ref>The catalyst is based on [[molybdenum(V) chloride]] and [[tris(2-aminoethyl)amine]] substituted with three very bulky hexa-isopropylterphenyl (HIPT) groups. Nitrogen adds end-on to the molybdenum atom, and the bulky HIPT substituents prevent the formation of the stable and nonreactive Mo-N=N-Mo [[ثنائي الوحدات|dimer]], and the nitrogen is reduced in an isolated pocket. The proton donor is a [[pyridinium]] cation, which is accompanied by a [[tetraborateبورات]] counter ion. The [[مختزل|reducing agent]] is [[decamethylchromocene]]. All ammonia formed is collected as the HCl salt by trapping the distillate with a HCl solution</ref><ref>Note also that, although the dinitrogen complex is shown in brackets, this species can be isolated and characterized. Here the brackets do not indicate that the intermediate is not observed.</ref> However, this catalytic reduction fixates only a few nitrogen molecules.