Tetrazenes cation

The oxidation potential of (396) is 570 mV anodic of (398), attributable to charge repulsion in the cw-tetrazene cation. 

In the medium pH range where both the diazenium cation and the diazene exist in solution, these two species react rapidly to afford a substituted tetrazene [141], The second oxidation wave, observed for disubstituted hydrazenes in acetonitrile with a pyridine base present, is due to the further oxidation of the tetrazene to a dicationic species. 

In the first stage of the reaction an alkoxyl anion and the nitrohydrazine cation are formed which afterwards react together to give the corresponding alcohol and nitrohydrazine. Nitrohydrazine reacts with excess hydrazine to produce tetrazene, nitrous acid and di-imid. Then the tetrazene decomposes to form ammonia and nitrogen from di-imid on the other hand tetrazene, hydrazine and nitrogen are formed. Hydrazoic acid and ammonia are then formed as decomposition products of tetrazene. 

Complexes (38) to (41) illustrate mononuclear Ir(I) complexes with N-donor ligands. The N2 ligand in (38) is introduced by the reaction of ArC(0)NNN with trans-IrCl(CO)(PPh3)2, and it is bound in an end-on fashion see End-On Coordination). Cation (39) contains Ir(III) and is formed from the neutral triazenido Ir(I) complex Ir(CO)(PPh3)(ArNNNAr) (Ar = aryl). The tetrazene ligand in (38) is a 4-electron donor, and complex (38) is an 18-electron complex. Pyrazine can act as a monodentate (41) or a bridging (42) ligand. ... 

Aliphatic amines are mainly converted to a-substituted products [99,100], whereby especially the a-methoxylation leads to valuable reagents for synthesis. The intermediate iminium salts can be directly trapped by silyl enol ethers to form Mannich bases [108]. If the a-position is blocked or steric conditions favor it, N,N coupling to hydrazo or azo compounds occurs (Table 5, numbers 17-19). 1,1-Disubstituted hydrazines are dimerized to tetrazenes in fair to excellent yields (Table 5, numbers 20-24). The intermediate diaze-nium ions can attack enolizable carbonyl compounds to form aza-Mannich bases [109]. Arylazonaphthols undergo anodic oxidation, producing radical cations. These couple to biphenylbisazo compounds (up to 34%) or can be trapped by anisidine to form azodiphe-nylamines (up to 74%) [110a]. 

The mechanism of nucleophilic amination presented by Eq. (73) seems very unlikely at first because of the instability of the azolyl cation and the low basicity of the N-amino group in Af-aminoazoles. However, the previously mentioned formation of arylazides from 1-aminobenzimidazole and aryldiazonium salts [Eq. (64)] is concerned, in fact, with such a process. Probably, the course of this reaction is governed also by the elimination of the azolyl fragment as the anion, which is due to the primary deprotonation of tetrazene 260. 

Tetramesityldisilene, 104 Tetramethylcyclobutadiene, 296 Tetrazenes, 118 Thiirane, 253 cation, 253 Thiiranes... 

Structural abbreviations for examples of the nonhydrazine couples studied appear in Chart 10.2. The only two trialkylamines with radical cation lifetimes long enough to study are l,4-diazabicyclo[2.2.2]octane, N[222]N, and Alder s tris-trimethylene bridged diamine N[333]N. Three tetraaIkyl-2-tetrazenes (abbreviated N4, preceded... 

---