cis-diazene	trans-diazene

Diazene, also called diimine or diimide, is a compound having the formula HN=NH. Azo compounds can be considered to be formally derived from diazene by substituting the hydrogen atoms with organyl groups. Azo compounds are compounds bearing the Functional group R-N=N-R' in which R and R' can be either Aryl or Alkyl. Because each nitrogen atom bears one hydrogen and one lone pair and double bonds cannot rotate, diazene exists in distinct cis and trans geometric isomers. lone pair is a (valence electron pair without bonding or sharing with other Atoms They are found in the outermost Electron shell of an atom so lone pairs Trans-2-butenesvg|right|thumb|Trans-2-butene]] In Chemistry, cis-trans isomerism or geometric isomerism or configuration isomerism is a form of

cis-Diazene is also a useful reagent in organic synthesis, as it can be used to hydrogenate alkenes, alkynes and polyenes, with selective delivery of hydrogen from one face of the substrate. This gives the same stereoselectivty as metal-catalysed syn addition of H₂. The advantages of using Diazene, however, are that there is no need for high pressures or potentially explosive hydrogen gas (the only gas released is relatively inert nitrogen) and no need for expensive metal catalysts.

Mechanism:

Diazene can be efficiently generated in-situ by elimination of sulfonohydrazides using a suitable base. For example 2,4,6-Triisopropylbenzenesulfonohydrazide can eliminate to give diazene using sodium hydrogen carbonate, a very mild base. Sodium bicarbonate or sodium hydrogen carbonate is the Chemical compound with the formula NaHCO3 This generates both the cis and trans forms of diazene and the isomerisation is slow. However, the trans - cis equilibrium is driven to the right due to the rapid consumption of the cis isomer by reaction with the substrate.

References

• Wiberg, E. ; Holleman, A. F. (2001). "1. 2. 7: Diimine, N₂H₂", Inorganic Chemistry. Elsevier, 628. Elsevier, the world's largest Publisher of Medical and Scientific literature, forms part of the Reed Elsevier group  
• Miller, Charles E. Hydrogenation with diimide. Journal of Chemical Education (1965), 42(5), 254-9. CODEN: JCEDA8 ISSN:0021-9584. [1]
• Trost et al Journal of the American Chemical Society 127 11 2005 3667 DOI:10. 1021/ja042435i[2]