Isodiazomethane

In organic chemistry, isodiazomethane, also known as isocyanamide, aminoisonitrile, or systematically as isocyanoamine,[1] is the parent compound of a class of derivatives of general formula R2N–NC. It has the condensed formula H2N–N+≡C–, making it an isomer of diazomethane. It is prepared by protonating an ethereal solution of lithiodiazomethane, LiCHN2, with aqueous NaH2PO4 or NH4Cl.[2] The parent compound is only marginally stable at room temperature and is isolated by removal of solvent at –50 °C.[3] Derivatives are generally prepared by dehydration of the corresponding substituted formylhydrazine with COCl2 and Et3N.[4]

Isodiazomethane

Resonance forms of isodiazomethane
Identifiers
3D model (JSmol)
ChemSpider
Properties
CH2N2
Molar mass 42.041 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Earlier, the compound was misidentified as the isomeric nitrilimine, HN––N+≡CH. However, this structure was disproven by 1H NMR studies, which show a compound with a single signal at δ 6.40 ppm in (CD3CD2)2O instead of two signals expected for nitrilimine. Moreover, an infrared band at 2140 cm−1 was assigned to the isocyano group. Transition metal complexes of isodiazomethane have been prepared.[5] In bulk form isodiazomethane is a liquid which decomposes when the temperature exceeds 15 °C. If it is heated to 40 °C, the substance explodes.[6] A solution of isodiazomethane in diethyl ether at –30 °C gradually isomerizes to diazomethane upon exposure to sodium hydroxide for 20 min.[4]

Microwave spectroscopy indicates that unlike diazomethane, isodiazomethane is not completely planar, with the amino nitrogen undergoing inversion.[7] An ab initio study indicated that there is some N–N double bond character in H2N–N≡C, although less so than in the N–C bond of H2N–C≡N.[8] Like other isocyanide derivatives and carbon monoxide, its primary resonance form carries a negative charge and lone pair on carbon, a comparatively rare situation for neutral molecules. A resonance form with zero formal charge on all atoms also has some importance; however, the carbon atom only has a sextet of electrons and is formally a carbene.

References
  1. Pubchem. "Aminoazaniumylidynemethane". pubchem.ncbi.nlm.nih.gov. Retrieved 2018-12-21.
  2. Moderhack, Dietrich (2012-07-29). "N-Isocyanides—synthesis and reactions". Tetrahedron. 68 (30): 5949–5967. doi:10.1016/j.tet.2012.04.099. ISSN 0040-4020.
  3. Anselme, J. P. (1966-11-01). "The chemistry of isodiazomethane". Journal of Chemical Education. 43 (11): 596. doi:10.1021/ed043p596. ISSN 0021-9584.
  4. Anselme, J.-P. (1977-05-01). "Isodiazomethane revisited. N-aminoisonitriles". Journal of Chemical Education. 54 (5): 296. doi:10.1021/ed054p296. ISSN 0021-9584.
  5. Fehlhammer, Wolf Peter; Buračas, Peter; Bartel, Klaus (1977). "Isodiazomethane Complexes". Angewandte Chemie International Edition in English. 16 (10): 707. doi:10.1002/anie.197707071. ISSN 1521-3773.
  6. Bretherick, L. (2013). Bretherick's Handbook of Reactive Chemical Hazards. Butterworth-Heinemann. p. 147. ISBN 9781483284668.
  7. Schäfer, Eckhard; Winnewisser, Manfred; Christiansen, Jørn Johs. (15 July 1981). "Millimeter-wave spectrum of isocyanamide, H2N-NC". Chemical Physics Letters. 81 (2): 380–386. doi:10.1016/0009-2614(81)80273-4.
  8. Ichikawa, Kazuo; Hamada, Yoshiaki; Sugawara, Yoko; Tsuboi, Masamichi (15 November 1982). "Ab initio study on cyanamide and isocyanamide". Chemical Physics. 72 (3): 301–312. doi:10.1016/0301-0104(82)85127-6.
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