Iron complexes azido

The 19-azido (93) and 19-methylthio (94) 4-androstene-3,17-diones have been found to be potent competitive reversible inhibitors (Kj = 5 nM and /fj = 1 nM respectively, for (androstenedione) = 25 nM). The same workers also discovered that 19-methanesulphonylthioandrostene-3,17-dione (95) inactivates AR in the presence of NADPH and Oj, although no kinetic or inhibitory data were presented [213]. The interaction of (94) with the active site was found to differ from that of (95) in that the latter displaces the substrate steroid from its binding site and on metabolism deactivates the enzyme, whereas (94) interacts with the substrate binding site but also with the haem-iron complex via a postulated coordinate bond. The differences in binding were deduced by examination of the ultraviolet spectral changes induced by the addition of the two inhibitors to the AR enzyme preparation. 

The product in the reaction of iron(n) with the azide radical at pH 5.6 is a hydrolysed iron(iii)-azido-complex. A zero-order dependence on iron(n) in the rate law for formation of the product is inconsistent with an inner-sphere redox process, and the proposed mechanism. 

In 1987, Nitta reported the formation of an unexpected vinylketene complex from the reaction of an azido-substituted cyclopropene with diiron nonacarbonyl.104 They had previously investigated the chemical behavior of the complexed nitrene intermediates that result from the reaction of organic azides and iron carbonyls113 and were interested in replicating the thermal isomerization of 3-azido-l,2,3-triphenylcyclopropene (163) into 4,5,6-triphenyl-l,2,3-triazine using a metal carbonyl-promoted re-... 

Another interesting point is the relative rates of the reactions of the azido and thiocyanatopentaammines. The relative rates of these two reactants with iron (I I) ion are similar to those with chromium (I I), that is, the azide is four to five powers of ten more rapid than is the thiocyanato. I am suggesting that this might be a criterion for inner sphere activated complex as opposed to an outer sphere complex. With trisdipyridylchromium(II) ion, which must react via an outer sphere process, the azido and thiocyanato rates are relatively comparable, and the same also for vanadium (I I) ion which also probably procedes via an outer sphere activated complex. 

The explosive properties of a series of 5 amminecobalt(III) azides were examined in detail. Compounds were hexaamminecobalt triazide, pentaammineazidocobalt diazide, cis- and traw.v-tetraamminediazidocobalt azide, triamminecobalt triazide [1], A variety of hydrazine complexed azides and chloroazides of divalent metals have been prepared. Those of iron, manganese and copper could not be isolated cobalt, nickel, cadmium and zinc gave products stable at room temperature but more or less explosive on heating [2]. Some polyammine azido-metal nitrates of Cr, Ni and Cu were found to be explosively photosensitive. Replacement of ammonia by triethanolamine gave compounds smoothly photodecomposing [3]. 

However, it remains to be determined whether the azido group is already coordinating the iron(ni), since the ligand field splitting is smaller compared to that of the resting azido complex. The other possibility is that the azide is not coordinating the iron but perturbs interactions between the iron-aqua ligand and its distal-pocket environment. 

These claims are not realistic [51-53] indeed, although certain cation impurities are removed from sodium azide, it contains foreign anions that are carried through. Also, the exchange resins themselves contain cation impurities, notably iron and copper, which are complexed and eluted as anionic azido complexes, thus introducing new impurities. One of them is the built-in red indicator, namely, azidoiron anions. Their chemical composition and retention on the resin, however, depend on the ionic strength (concentration) of the eluent, and elution at the point of proton exhaustion would be coincidental. 

Interaction with the second iron centre can be prevented by using a porphyrin ligand with bulky substituents. An example is ligand 29.10, a so-called picket-fence porphyrin. An example of a model complex containing [Fe(29.10)] with an azido ligand bound to the iron(II) centre is shown in Fig. 29.9. Studies of such models provide information about the properties of high-spin iron(II) porphyrinato complexes. The four substituents in ligand 29.10 form a cavity, and reaction 29.6 shows the... 

Cyclic P-ketoesters were converted to the corresponding products in high yields with up to 93% ee catalyzed by the combination of iron(II) chloride complex and silver carboxylate. 3-Azido aryl oxindoles were obtained with up to 94% ee using the catalyst prepared by iron(II) propionate and the ligand in situ (Scheme 15.10). 

A related reaction was published by Akita et al azide reacts with the cationic cyclo-pentadienyliron complex [(77 -Cp)Fe(CO)2(r/ -Ph-C=C-Ph)] by attacking the central C=C triple bond to form the organoazide derivative dicarbonyl(77 -cyclopentadienyl)(/ ran -l,2-diphenyl-2-azidoethenyl)iron(II) (Figure 12.7). The ran -configuration of the C=C double bond seems to enhance the stability of the vinyl azide as shown by Fowler et al for azido-l,2-diphenylethene. ... 

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