Diimides disproportionation

In the absence of a substrate, diimide disproportionates to nitrogen and hydrazine, which combines with the ketene formed to give acetylhydrazide. 

The reduction of N2 could occur either via a similar way as described above by Eqs.(25a)—(25 d) or by special stabilization of the diimid and its subsequent direct reduction to NH3 via N2H4, thus avoiding diimid-disproportionation. 

Diimide can act as both a hydrogen acceptor and donor, undergoing disproportionation as a side-reaction which produces a considerable amount of nitrogen gas. From a practical point of view the occurrence of this disproportionation reaction requires the use of an excess of the diimide precursor. 

During diimide reductions considerable nitrogen gas is formed by the disproportionation of diimide. Theoretical calculations on the energy surfaces for the transfer of hydrogen from c s-diimide to cis- and... 

A limitation to the use of diimide as a reducing agent appears to be the relative rate at which diimide reacts with the unsaturated substrate. If the rate of reduction is sufficiently slower than that of the disproportionation of diimide, the latter reaction will dominate and no reduction will be accomplished. A fur-... 

Diimide occurs only as an unstable intermediate in the hydrolysis of azodi-carboxylic acid, in the alkaline cleavage of benzene sulfonyl hydrazide, hydroxyl-amine-O-sulfonic acid and chloramine, in the oxidation of hydrazine, and in several other organic decomposition reactions . At room temperature it readily undergoes decomposition, disproportionation, and in the presence of symmetrical multiple bonds (like the ones in olefins) hydrogen transfer reactions ... 

Diimide reductions typically require an excess of the diimide-generating reagents, because part of the diimide formed is lost to disproportionation ... 

Ab initio SCF calculations on disproportionation reactions of diimide (N2H2) to form hydrazine and dinitrogen have been concerned with concerted hydrogen transfer pathways between cis and cis forms and cis and trans forms, but a two-step hydrogen atom transfer process involving N2H and N2H3 radicals was shown to be energetically feasible. 

Unfortunately, reaction with the olefinic precursor of the PLA2-inhibitor 324 (see also Section 4.1.1) was found to be incomplete even after 36 h. The radiochemical yield was very low, with only 74 mCi of325 obtained from the use of 10.9 Ci of carrier-free tritiated water. This may result from partial loss of [ HJdiimide through disproportionation to [ H]-hydrazine and nitrogen, so that an excess of diimide may be required to achieve good product yields . ... 

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