Diimide

Source: Wikipedia, the free encyclopedia.
Not to be confused with
Diazane.
See also: azo compound
Diimide
Ball and stick model of diazene ((E)-diazene)
Ball and stick model of diazene ((E)-diazene)
E/trans-diazene
Structural formula of diazene ((E)-diazene)
Structural formula of diazene ((E)-diazene)
Structural formula of diazene ((Z)-diazene)
Structural formula of diazene ((Z)-diazene)
Z/cis-diazene
Ball and stick model of diazene ((Z)-diazene)
Ball and stick model of diazene ((Z)-diazene)
Names
IUPAC name
Diazene
Other names
Diimide
Diimine
Dihydridodinitrogen
Azodihydrogen
Identifiers
3D model (
JSmol
)
ChEBI
ChemSpider
KEGG
MeSH Diazene
UNII
  • InChI=1S/H2N2/c1-2/h1-2H checkY
    Key: RAABOESOVLLHRU-UHFFFAOYSA-N checkY
  • InChI=1/H2N2/c1-2/h1-2H
    Key: RAABOESOVLLHRU-UHFFFAOYAG
  • N=N
Properties
H2N2
Molar mass 30.030 g·mol−1
Appearance Yellow gas
Melting point −80 °C (−112 °F; 193 K)
Related compounds
Other anions
 diphosphene
dinitrogen difluoride
Other cations
 azo compounds
Related Binary azanes
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)

Diimide, also called diazene or diimine, is a compound having the formula HN=NH. It exists as two

geometric isomers, E (trans) and Z (cis). The term diazene is more common for organic derivatives of diimide. Thus, azobenzene
is an example of an organic diazene.

Synthesis

A traditional route to diimide involves oxidation of hydrazine with hydrogen peroxide or air.[1]

N2H4 + H2O2 → N2H2 + 2H2O

Alternatively the hydrolysis of diethyl azodicarboxylate or azodicarbonamide affords diimide:[2]

Et−O2C−N=N−CO2−Et → HN=NH + 2 CO2 + 2 HOEt

Nowadays, diimide is generated by thermal decomposition of 2,4,6‐triisopropylbenzenesulfonylhydrazide.[3]

Because of its instability, diimide is generated and used in-situ. A mixture of both the cis (Z-) and trans (E-) isomers is produced. Both isomers are unstable, and they undergo a slow interconversion. The trans isomer is more stable, but the cis isomer is the one that reacts with unsaturated substrates, therefore the equilibrium between them shifts towards the cis isomer due to

nitrogen gas:[5]

2 HN=NH → H2N−NH2 + N2

Because of this competing decomposition reaction, reductions with diimide typically require a large excess of the precursor reagent.

Applications to organic synthesis

Main article: Reductions with diimide

Diimide is occasionally useful as a reagent in organic synthesis.[4] It hydrogenates alkenes and alkynes with selective delivery of hydrogen from one face of the substrate resulting in the same stereoselectivity as metal-catalysed syn addition of H2. The only coproduct released is nitrogen gas. Although the method is cumbersome, the use of diimide avoids the need for high pressures or hydrogen gas and metal catalysts, which can be expensive.[6] The hydrogenation mechanism involves a six-membered C2H2N2 transition state:

Mechanism of hydrogenation using diimide.

Selectivity

Diimide is advantageous because it selectively reduces alkenes and alkynes and is unreactive toward many

alkyl halides, and thiols are tolerated by diimide, but these same groups would typically be degraded by metal catalysts. The reagent preferentially reduces alkynes and unhindered or strained alkenes[1] to the corresponding alkenes and alkanes.[4]

Related

The dicationic form, H−N+≡N+−H (diazynediium, diprotonated dinitrogen), is calculated to have the strongest known chemical bond. This ion can be thought of as a doubly protonated nitrogen molecule. The relative bond strength order (RBSO) is 3.38.[7] F−N+≡N+−H (fluorodiazynediium ion) and F−N+≡N+−F (difluorodiazynediium ion) have slightly lower strength bonds.[7]

In the presence of strong bases, diimide deprotonates to form the pernitride anion, N−=N−.

References

  1. ^ a b Ohno, M.; Okamoto, M. (1973). "cis-Cyclododecene". Organic Syntheses; Collected Volumes, vol. 5, p. 281.
  2. ISBN 9780123526519
    .
  3. ISBN 978-0471936237
    .
  4. ^
    ISBN 0471936235
    .
  5. ISBN 978-0123526519
    .
  6. doi:10.1021/ed042p254
    .
  7. ^
    S2CID 11884042
    .
Retrieved from "https://en.wikipedia.org/w/index.php?title=Diimide&oldid=1217918939"