Main-group element-mediated activation of dinitrogen

Main-group element-mediated activation of dinitrogen refers to the conversions of N2 by main group element compounds. The number of main group compounds derived from dinitrogen are few compared to the number of transition metal-based systems.[1] In neither the main group nor the transition metal cases has any molecular compound proved useful. A commercial example of a main-group element-mediated activation of dinitrogen is the Frank–Caro process for the production of calcium cyanamide from calcium carbide.

Activation by lithium

Metallic lithium burns in an atmosphere of nitrogen, giving lithium nitride.[2][3] Hydrolysis of the resulting nitride gives ammonia. In a related process, trimethylsilyl chloride, lithium and nitrogen react in the presence of a catalyst to give tris(trimethylsilyl)amine, which can be further elaborated.[4] Processes that involve oxidising the lithium metal are however of little practical interest, since they are non-catalytic and re-reducing the Li+
 ion residue is difficult. The hydrogenation of Li3N to produce ammonia has seen some exploration since the resulting lithium hydride can be thermally decomposed back to lithium metal.[5]

Activation by calcium

The Frank–Caro process is a commercial nitrogen fixation process involving the activation of N2 by calcium carbide. The conversion occurs at about 1,000 °C. The reaction is exothermic and self-sustaining once the reaction temperature is reached. Originally the reaction was conducted in large steel cylinders with an electrical resistance element providing heat to start the reaction. Modern production uses rotating ovens.[6]

CaC2 + N2 → CaCN2 + C

Turning to molecular calcium chemistry, reduction of an iodo calcium(II) complex [CaI(BDI)]2 in the presence of THF under N2 gives [Ca(BDI)]2N2. The N-N distances in this product (1.258(3) and 1.268(3) Å) are much longer than that of the dinitrogen triple bond (1.098 Å) and comparable to other N=N double bonds.[7]

Activation by boron

2-Electron reduction of [(CAAC)BDurBr2] induces binding of dinitrogen (CAAC = cyclic alkyl amino carbenes, Dur = durenyl).[8] The initial step is proposed to involve a borylene radical binding to N2. The dipotassium complex {[(CAAC)DurB]2(μ2-N2K2)} was characterized by X-ray crystallography. Air-oxidation of the dipotassium complex gives the bis(borylene) diimide {[(CAAC)DurB]2(μ2-N2)}. Hydrolysis of the dipotassium compound gives the diradical {[(CAAC)DurB]2(μ2-N2H2)}. Further protonation and reduction of {[(CAAC)DurB]2(μ2-N2H2)} results in cleavage of the central N-N bond.[9]

Repeating the same reaction but replacing Dur (2,3,5,6-tetramethyl-phenyl) by a bulkier Tip (2,4,6-triisopropylphenyl) group resulted in a different result, the product being {[(CAAC)-TipB]2(μ2-N4K2)}. The product contains an N4 chain.[10]

N2 can be activated by in situ generated boron-centered radicals.[11]

Activation by carbon

Carbene species have also been considered as a means to bind N2. The reaction of interest is the reverse of the decomposition of diazoalkanes with the release of N2.[12] For example, bromo(trifluoromethyl)carbene was shown to bind N2 to give 3-bromo-3-(trifluoromethyl)diazirines at low temperatures in an argon matrix.[13]

References

  1. ^ Tanabe, Yoshiaki; Nishibayashi, Yoshiaki (2024). "Catalytic Nitrogen Fixation Using Well-Defined Molecular Catalysts under Ambient or Mild Reaction Conditions". Angewandte Chemie International Edition. 63 (33) e202406404. doi:10.1002/anie.202406404. PMID 38781115.
  2. ^ Rabenau, A.; Schulz, Heinz (1976-11-01). "Re-evaluation of the lithium nitride structure". Journal of the Less Common Metals. 50 (1): 155–159. doi:10.1016/0022-5088(76)90263-0. ISSN 0022-5088.
  3. ^ Roy, Debjani; Navarro-Vazquez, Armando; Schleyer, Paul. v. R. (2009-08-24). "Modeling Dinitrogen Activation by Lithium: A Mechanistic Investigation of the Cleavage of N2 by Stepwise Insertion into Small Lithium Clusters". Journal of the American Chemical Society. 131 (36): 13045–13053. Bibcode:2009JAChS.13113045R. doi:10.1021/ja902980j. ISSN 0002-7863. PMID 19702311.
  4. ^ Brook, Michael A. (2000). Silicon in Organic, Organometallic, and Polymer Chemistry. New York: John Wiley & Sons, Inc. pp. 193–194.
  5. ^ Goshome, Kiyotaka; Miyaoka, Hiroki; Yamamoto, Hikaru; Ichikawa, Tomoyuki; Ichikawa, Takayuki; Kojima, Yoshitsugu (2015). "Ammonia Synthesis via Non-Equilibrium Reaction of Lithium Nitride in Hydrogen Flow Condition". Materials Transactions. 56 (3): 410–414. doi:10.2320/matertrans.M2014382. ISSN 1345-9678.
  6. ^ Thomas Güthner; Bernd Mertschenk (2006). "Cyanamides". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a08_139.pub2. ISBN 3527306730.
  7. ^ Rösch, B.; Gentner, T. X.; Langer, J.; Färber, C.; Eyselein, J.; Zhao, L.; Ding, C.; Frenking, G.; Harder, S. (2021-03-12). "Dinitrogen complexation and reduction at low-valent calcium". Science. 371 (6534): 1125–1128. Bibcode:2021Sci...371.1125R. doi:10.1126/science.abf2374. ISSN 0036-8075. PMID 33707259. S2CID 232199834.
  8. ^ Légaré, Marc-André; Bélanger-Chabot, Guillaume; Dewhurst, Rian D.; Welz, Eileen; Krummenacher, Ivo; Engels, Bernd; Braunschweig, Holger (2018-02-23). "Nitrogen fixation and reduction at boron". Science. 359 (6378): 896–900. Bibcode:2018Sci...359..896L. doi:10.1126/science.aaq1684. ISSN 0036-8075. PMID 29472479. S2CID 3460701.
  9. ^ Légaré, Marc-André; Bélanger-Chabot, Guillaume; Rang, Maximilian; Dewhurst, Rian D.; Krummenacher, Ivo; Bertermann, Rüdiger; Braunschweig, Holger (November 2020). "One-pot, room-temperature conversion of dinitrogen to ammonium chloride at a main-group element". Nature Chemistry. 12 (11): 1076–1080. Bibcode:2020NatCh..12.1076L. doi:10.1038/s41557-020-0520-6. ISSN 1755-4349. PMID 32929247. S2CID 221674637.
  10. ^ Légaré, Marc-André; Rang, Maximilian; Bélanger-Chabot, Guillaume; Schweizer, Julia I.; Krummenacher, Ivo; Bertermann, Rüdiger; Arrowsmith, Merle; Holthausen, Max C.; Braunschweig, Holger (2019-03-22). "The reductive coupling of dinitrogen". Science. 363 (6433): 1329–1332. Bibcode:2019Sci...363.1329L. doi:10.1126/science.aav9593. ISSN 0036-8075. PMID 30898929. S2CID 85448379.
  11. ^ Bennaamane, Soukaina; Rialland, Barbara; Khrouz, Lhoussain; Fustier-Boutignon, Marie; Bucher, Christophe; Clot, Eric; Mézailles, Nicolas (2022-10-27). "Ammonia Synthesis at Room Temperature and Atmospheric Pressure from N2: A Boron-Radical Approach". Angewandte Chemie International Edition. 62 (3) anie.202209102. doi:10.1002/anie.202209102. ISSN 1433-7851. PMC 10107438. PMID 36301016. S2CID 253158973.
  12. ^ Shilov, A. E.; Shteinman, A. A.; Tjabin, M. B. (1968-01-01). "Reaction of carbenes with molecular nitrogen". Tetrahedron Letters. 9 (39): 4177–4180. doi:10.1016/S0040-4039(00)75402-5. ISSN 0040-4039.
  13. ^ O'Gara, John E.; Dailey, William P. (May 1992). "Direct observation, reactions under matrix-isolation conditions, and ab initio calculations for halo(trifluoromethyl)carbenes. Evidence for the photochemical addition of a carbene to dinitrogen". Journal of the American Chemical Society. 114 (10): 3581–3590. Bibcode:1992JAChS.114.3581O. doi:10.1021/ja00036a001. ISSN 0002-7863.
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