Dinitrogen iron complexes

NSiQHn, tert-Butylamine, iV-(trimethyl-silyl)-, 25 8 N2, Dinitrogen iron complexes, 24 208, 210 osmium complex, 24 270 N2BC4H, Borane, cyano-compd. with trimethylamine (1 1),... 

The nitrosation of primary alkylamines leads to deamination products. Hungarian chemists (Dozsa et al., 1984 Katho et al, 1984 Katho and Beck, 1988) investigated the kinetics by spectrophotometry and by N2-volumetric measurements in aqueous solution at pH 8.6-10.2. The results are consistent with the mechanism (4-4), in which an alkyldiazenido-iron complex 4,5 is formed followed by its decomposition to the dinitrogen-iron complex 4,6 by attack of hydroxyl ions. In the opinion of the present author, however, there are other mechanisms that would also support the kinetic data. 

The same [bis(imino)pyridine][bis(dinitrogen)]iron complex [( PDI)Fe(N2)2] also catalyzes the reductive cyclization of l,6-en5mes and diynes to afford cyclopentanes with exocyclic double bonds in the presence of hydrogen (Scheme 4-302)J ... 

Scheme 4-331. Hydrogenation of (+)-(/ )-limonene catalyzed by a [bis(imino)pyridine]bis(dinitrogen)iron complex.

Bis(imino)pyridine]bis(dinitrogen)iron complexes such as [( PDI)Fe(N2)]2(p2-N2) are active catalysts for the hydrogenation of a,P-unsaturated esters (Scheme 4-334). The efficiency of the catalyst can be adjusted by the substitution pattern of the aryl moiety. The dimethylaiyl substituent shown is superior to the corresponding ethyl or isopropyl derivatives. Bis(imino)pyridines with phenyl substituents in the imine backbone exhibit a much reduced activity to alkene hydrogenation as they are prone to carbonyl coordination. ... 

Scheme 4-337. Hydrosilylation of alkenes catalyzed by an bisimino(dinitrogen)iron complex.

With the same tactic, a meta-stable 3-coordinate iron(III) imido complex was reported by Holland and coworkers [40]. Using the diketiminate-supported dinitrogen iron(I) complex [L T eNNFeU ] as a source of iron(I) precursor [L = 2,4-bis (2,6-diisopropylphenylimino)pent-3-yl], the addition of adamantyl azide (AdN3) in... 

The suggestion for the catalytic cycle is presented in Scheme 4.18. Initially, an unsaturated iron complex is formed by expulsion of both dinitrogen molecules. Next, coordination of the alkene takes place, which is preferred since activation of hydrogen is also feasible. After alkene coordination, oxidative addition of hydrogen yields a formally 18-electron complex. Insertion of the alkene gave an alkyl complex, which recreated the starting complex via reductive elimination. Notably, the alkene complex also supports an isomerization of the double bond, hence an extension of possible intermediates is conceivable. 

Hazari N. Homogeneous iron complexes for the conversion of dinitrogen into ammonia and hydrazine. Chem Soc Rev. 2010 39 4044-56. 

Zero-valent iron complexes can activate small molecules. For example, reduction of FeCl2(diphos)2 under nitrogen atmosphere resulted in formation of Fe(N2)(diphos)2 [diphos = dmpe or depe] (Scheme 10.13). Interestingly protonolysis of Fe(N2)(dmpe)2 was reported to give ammonia under ambient conditions [75]. In addition, the coordinated dinitrogen in Fe(N2)(depe)2 [76-77] can be readily replaced with CO or CO2. 

The enzymology and biochemistry of nitrogenases started only a few years before the first dinitrogen metal complex was discovered by Allen and Senoff in 1965. Cooperation and mutual encouragement increased when more and more results were found on both sides. Two iron-sulfur proteins are involved in the nitrogenase complex. The larger protein, the nitrogenase itself, consists of four subunits and has an... 

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