Tetrazane, tetrazene, and tetrazadiene complexes

Organic derivatives of tetrazane ( buzane ) H2N—NH—NH—NH2 have been known since 1893 (227), but to date no transition metal tetrazane complexes have been fully characterized. However, iron tetrazane species have been proposed as intermediates in the iron(II)-catalyzed aerobic oxidation of hydrazines (104,230) and are thought to account for the red coloration observed in some of these reactions (230). 

In contrast, tetrazadienes, RN=N—N=NR, which are unknown in the free state, are found in a growing number of transition metal complexes. The ligands can be generated in situ from organic azides or diazonium cations and, following the discovery of Fe(MeNNNNMeXCO)3 by Dekker and Knox in 1967 (59), an extensive range of transition metal tetrazadiene complexes has been synthesized. Finally, several papers report theoretical calculations on the stability and structure of N4 ligands bound to transition metals (196-198). 

Tetrazane complexes may form as unstable intermediates during the transition metal catalyzed oxidation of hydrazines. Tetrazene adducts are 

Reactions involving transfer of tetrazadiene ligands between metal centers have also been reported (170). 

Tetrazadiene complexes are noted for their brilliant color and for their stability, which is much greater than that of analogous 1,4-diazabutadiene derivatives. 

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