Isodiazomethane
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| ImageFile = Isodiazomethaneresonance.png
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| ImageCaption = Resonance forms of isodiazomethane
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| Section1 = {{Chembox Identifiers
| CASNo = 4702-38-9
| SMILES = [C-]#[N+]N
| InChI=1S/CH2N2/c1-3-2/h2H2
| InChIKey = DOIJUTUOUQGQPQ-UHFFFAOYSA-N
| PubChem = 20684874
| ChemSpiderID = 19474507
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| Section2 = {{Chembox Properties
| C=1|H=2|N=2
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In organic chemistry, isodiazomethane, also known as isocyanamide, aminoisonitrile, or systematically as isocyanoamine,{{Cite web|url=https://pubchem.ncbi.nlm.nih.gov/compound/20684874|title=Aminoazaniumylidynemethane|last=Pubchem|website=pubchem.ncbi.nlm.nih.gov|language=en|access-date=2018-12-21}} 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.{{Cite journal|date=2012-07-29|title=N-Isocyanides—synthesis and reactions|journal=Tetrahedron|language=en|volume=68|issue=30|pages=5949–5967|doi=10.1016/j.tet.2012.04.099|issn=0040-4020|last1=Moderhack|first1=Dietrich}} The parent compound is only marginally stable at room temperature and is isolated by removal of solvent at –50 °C.{{Cite journal|last=Anselme|first=J. P.|date=1966-11-01|title=The chemistry of isodiazomethane|journal=Journal of Chemical Education|volume=43|issue=11|pages=596|doi=10.1021/ed043p596|bibcode=1966JChEd..43..596A|issn=0021-9584}} Derivatives are generally prepared by dehydration of the corresponding substituted formylhydrazine with COCl2 and Et3N.{{Cite journal|last=Anselme|first=J.-P.|date=1977-05-01|title=Isodiazomethane revisited. N-aminoisonitriles|journal=Journal of Chemical Education|volume=54|issue=5|pages=296|doi=10.1021/ed054p296|bibcode=1977JChEd..54..296A|issn=0021-9584}}
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.{{Cite journal|last1=Fehlhammer|first1=Wolf Peter|last2=Buračas|first2=Peter|last3=Bartel|first3=Klaus|date=1977|title=Isodiazomethane Complexes|journal=Angewandte Chemie International Edition in English|volume=16|issue=10|pages=707|doi=10.1002/anie.197707071|issn=1521-3773}} 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.{{cite book |last1=Bretherick |first1=L. |title=Bretherick's Handbook of Reactive Chemical Hazards |date=2013 |publisher=Butterworth-Heinemann |isbn=9781483284668 |page=147 |url=https://books.google.com/books?id=frz-BAAAQBAJ&pg=PA147 |language=en}} A solution of isodiazomethane in diethyl ether at –30 °C gradually isomerizes to diazomethane upon exposure to sodium hydroxide for 20 min.
Microwave spectroscopy indicates that unlike diazomethane, isodiazomethane is not completely planar, with the amino nitrogen undergoing inversion.{{Cite journal|last1=Schäfer|first1=Eckhard|last2=Winnewisser|first2=Manfred|last3=Christiansen|first3=Jørn Johs.|date=15 July 1981|title=Millimeter-wave spectrum of isocyanamide, H2N-NC|journal=Chemical Physics Letters|volume=81|issue=2|pages=380–386|doi=10.1016/0009-2614(81)80273-4|bibcode=1981CPL....81..380S}} 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.{{Cite journal|last1=Ichikawa|first1=Kazuo|last2=Hamada|first2=Yoshiaki|last3=Sugawara|first3=Yoko|last4=Tsuboi|first4=Masamichi|date=15 November 1982|title=Ab initio study on cyanamide and isocyanamide|journal=Chemical Physics|volume=72|issue=3|pages=301–312|doi=10.1016/0301-0104(82)85127-6|bibcode=1982CP.....72..301I}} 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.
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