Reactions Involving Ligated Diazenes

The formation of metal-bound diazene from dinitrogen and its subsequent disproportionation is a plausible mechanism of action of nitro-genase (54). The disproportionation of free diazene is well established (Section V,A) although such reactions of metal-bound diazene are as yet unknown. The enzymatic release of a reactive species such as cis-, trans-, or iso-diazene would be unexpected but cannot be ruled out. 

The synthesis of diazene complexes has been described (Sections V,B, C, and D). It is worth reiterating that no diazene complex has been prepared via reactions of coordinated dinitrogen and no stoichiometric conversion to hydrazine or ammonia has been demonstrated. 

Organodiazenes show a somewhat richer chemistry. Many years ago it was demonstrated that coordinated phenyldiazene can be catalyti-cally hydrogenated on platinum(O) according to Eq. (59) (268, 216). 

Recent work on the insertion of diazenido ligands into M—H bonds and on the attack of hydride and organolithium reagents upon diazenido complexes suggest that such reactions may be feasible (14). 

In summary, the chemistry of coordinated diazene and organo-diazenes is insufficiently developed to permit a detailed discussion of the role of diazene in the action of nitrogenase. 

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