Iron complexes diazenes

Figure 6.15 Iron-sulfur-diazene complexes as studied in reference 49.

Mahy JP, Gaspard S, Delaforge M et al (1994) Reactions of prostaglandin-H synthase with monosubstituted hydrazines and diazenes - formation of iron(II)-diazene and iron(III)-sigma-alkyl or iron(III)-sigma-aryl complexes. Eur J Biochem 226 445 157... 

The likelihood that alkyl radicals, like their aryl counterparts, bind to the iron before shifting to the nitrogen is supported by the observation that the type II complexes formed between alkyldiazenes and P450 in the absence of oxygen are converted, in the presence of limited amounts of oxygen, to complexes with an absorption maximum at 480 nm characteristic of iron-carbon o-bonded complexes Furthermore, alkyl diazene-iron tetraphenylporphyrin complexes can be prepared under anaerobic conditions. However, the alkyl-iron complexes are much less stable and less well characterized than the aryl-iron complexes and their involvement in heme iV-alkylation reactions remains to be demonstrated. 

Battioni, P., J.-P. Mahy, G. Gillet, and D. Mansuy (1983). Iron porphyrin dependent oxidation of methyl- and phenylhydrazine Isolation of iron(II)-diazene and sigma-alkyliron (III) (or aryliron(III)) complexes. Relevance to the reactions of hemopro-teins with hydrazines. J. Am. Chem. Soc. 105, 1399-1401. 

Iron carbonyl complexes are easily prepared by the reaction of Fe2(CO)9 with a cyclic diazene. An excess of the diazene prevents the more favoured formation of binuclear compounds29 3°). Trans-diazenes like trans-dimethyldiazene3 or azo-... 

From the fact that trans-diazenes do not form any of the complexes described, it may be concluded that the initial interaction of the N=N bond with the metal is largely determined by the symmetry of the HOMO (n i)89. Both trans and cis-diazenes possess similar ionisation potentials but only the latter have a HOMO of proper symmetry to overlap with the LUMO (dxy, d, dyz or dx2. y ) of the reacting iron carbonyl species. 

We investigated (82) two iron sulfur complexes with diazene (di-imide) as the sixth ligand, [Fe(NHS4)(N2H2)] = 1 (N2H2) and [Fe(S4)PR3 (N2H2)] = 2(N2H2)(Fig.3). 

The total electronic coordination energy of frans-diazene is —73.1 kJ/mol including the estimated total hydrogen bond energy of (—)20 kJ/mol for the mononuclear complex irons-2(N2H2) (see above). Thus, the stabilization of the unstable diazene ligand by hydrogen... 

Dieter Otto Sellmann Iron-diazene complex as model for enzymatic nitrogen fixation... 

The recently confirmed inhibition of cytochrome P-450 by Isoniazid and hydralazine does not result from heme alkylation but rather from the formation of a transient complex with an absorption maximum at 449 nm.41-44 xjjg complex and its inhibitory effect are dissipated by ferrl-cyanide. The Inhibition by isoniazid thus resembles that mediated by 1,1-disubstituted hydrazines, which also form reversible cytochrome P-450 complexes absorbing at 449 nm. 5 studies with metalloporphyrins indicate that 1,1-dialkyIhydrazines are oxidized to amlnonitrenes that coordinate to the iron atom. The coordination of diazene metabolites with the heme of cytochrome P-450 also yields complexes with an absorbance maximum at 446 nm. ... 

An argument for HD formation on bound diazene complexes has been elucidated. This idea is based on iron and ruthenium diazene complexes that readily exchange the protons from their //-N2H2 ligands with free H2. 

In contrast to their Fe(ii) congeners, Fe(i) or Fe(0) do activate N2 toward protonation. A first example was the so-called Leigh cycle, which involves the conversion of N2 to NH3 mediated by iron(O) phosphine complexes. In this context, Tyler and coworkers synthesized the complex [Fe(N2) (DMeO-PrPE)2] supported by the DMeOPrPE = l,2-bis[bis(methoxypropyl)phos-phinojethane ligand, which renders the iron-N2 complex water soluble. Based on this work, the reduction and protonation of N2 coordinated to the simpler Fe(dmpe)2 complex has been treated by DFT. In this work, three plausible mechanistic pathways were evaluated (1) symmetric protonation, where protons are added to each nitrogen in an alternating sequence proceeding through diazene and hydrazine intermediates (2) asymmetric... 

Crossland JL, Balesdent CG, Tyler DR. Intermediates in the reduction of N2 to NH3 synthesis of iron tl -hydrazido(l-) and diazene complexes. Dalton Trans. 2009 4420-4422. 

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