Iron complexes applications

In a review on the design of ligands for selective complexation of metal ions in aqueous media and a book on the principles underlying stability constants and on the design of metal complexes for various medical applications iron complexes and their solution chemistry take their appropriate place. 

Because there exist a number of reviews which deals with the structural and mechanistic aspects of high-valent iron-oxo and peroxo complexes [6,7], we focus in this report on the application and catalysis of iron complexes in selected important oxidation reactions. When appropriate we will discuss the involvement and characterization of Fe-oxo intermediates in these reactions. 

Hydride species were also formed in the dehydrogenative coupling of hydrosilanes with DMF [45]. The catalytic system is applicable to tertiary silanes, which are known to be difficult to be converted into disiloxanes (Fig. 17). The catalytic reaction pathway involves the intermediacy of a hydrido(disilyl)iron complex... 

Although there are some reactions that use complex 76 stoichiometrically [50-58], it was not until 1979 that Roustan et al. developed the first catalytic application of complex 76-Na (Scheme 16) [59, 60]. In his publication, he could show that catalytic amounts of complex 76-Na react with an allylic chloride or acetate to form an allyl-iron-complex, which, in a second step, is substituted with a malonate to yield 77. Most importantly, they observed a preference for the ipso-substitution-product 77a, that is, the new C-Nu-bond was formed preferentially at the carbon atom that was substituted with the leaving group before. 

However, one should view these matrix elements with great caution when it comes to their application within actual iron complexes. There are two main reasons for advising caution. 

Table 12.30 Suitability of various sulphur dye types for application with anthra-quinonoid or iron-complex redox systems [214]...

A viable iron carbonyl-mediated reduction process converts acid chlorides and bromoalkanes into aldehydes [3, 6]. Yields are high, with the exception of nitro-benzoyl chloride, and the procedure is generally applicable for the synthesis of alkyl, aryl and a,(i-unsaturated aldehydes from the acid chlorides. The reduction proceeds via the initial formation of the acyl iron complex, followed by hydride transfer and extrusion of the aldehyde (cf. Chapter 8). 

The reaction of the complex salt 6a with the arylamine 12 affords by regio-selective electrophilic substitution the iron complex 13 [88] (Scheme 11). The oxidative cyclization of complex 13 with very active manganese dioxide provides directly mukonine 14, which by ester cleavage was converted to mukoeic acid 15 [89]. Further applications of the iron-mediated construction of the carbazole framework to the synthesis of 1-oxygenated carbazole alkaloids include murrayanine, koenoline, and murrayafoline A [89]. 

As well as organic chiral auxiliaries, organometallic fragments have found some application as chiral auxiliaries in conjugate addition reactions. Particularly noteworthy are chiral molybdenum allyl complexes [69], chiral iron complexes [70], and planar chiral arene chromium species [71]. 

As an application of this procedure, Snapper succeeded in the formal total synthesis of (+)-astericanolide. Treatment of iron complex 62, which is prepared from cyclopentenol derivative 60 and iron complex 61, with MeaNO gives fused cyclobutene derivative 63. ROM of cyclobutene of 63 using Ig under ethylene gas smoothly proceeds to produce an eight-membered ring of 64 via Cope rearrangement. The resulting product 64 is converted into Wender s intermediate for the synthesis of (+)-astericanolide ... 

In the quinone imine cyclization of iron complexes to carbazoles, the arylamine-substituted tricarbonyl(ri -cyclohexadiene)iron complexes 571 are chemoselectively oxidized to a quinone imine 574 prior to cyclodehydrogenation. This mode of cyclization is particularly applicable for the total synthesis of 3-oxygenated tricyclic carbazole alkaloids (Scheme 5.25). 

Electrophilic aromatic substitution of 708 with the iron-coordinated cation 602 afforded the iron-complex 714 quantitatively. The iron-mediated quinone imine cyclization of complex 714, by sequential application of two, differently activated, manganese dioxide reagents, provided the iron-coordinated 4b,8a-dihydrocarbazole-3-one 716. Demetalation of the iron complex 716 with concomitant... 

As already briefly mentioned, the oxygen-atom insertion into Si—H bonds of silanes constitutes a selective method for the chemoselective preparation of silanols, which has been much less studied compared to the CH oxidation. This unique oxyfunctionalization of silanes is also highly stereoselective (equation 35) since, like the CH insertions, it proceeds with complete retention of configuration. A novel application of the SiH insertion process is the synthesis of the unusual iron complex with a silanediol functionality, in which selectively both Si—H bonds of the silicon atom proximate to the iron ligand are oxidized in the silane substrate (equation 36). ... 

Applying the pseudo-atom convention to the iron complex in Figure 8, the iodine atom is priority 1, the t1S-C5H3R2 ligand is priority number 2, the phosphorus atom is priority number 3, and carbon is priority number 4.15 When the iron is viewed from the side opposite the priority number 4, the sequence is 1,2,3 in the anticlockwise or 5 direction. The highest priority carbon in the cyclopentadienyl ligand, indicated by an asterisk, is designated with the R chirality symbol by application of the extended CIP sequence rule. 

Metal complexes of o-hydroxynitroso compounds are principally of historical interest since the iron complex of l-nitroso-2-naphthol (Pigment Green B Cl 10006), which still finds commercial application as a green pigment, is the oldest fully synthetic metal complex dyestuff, dating back... 

Shul pin and coworkers described the application of a di- and a tetranudear iron complex with triazacyclononane acetate ligands in the oxidation of alkanes and alcohols with H202 [47]. A highly complex tetranudear iron complex with octadentate pyridine carboxylate ligands was described by Gutkina et al. [48]. However, the TONs for cyclohexane oxidation did not exceed 5.0 in the latter case. 

The intermolecular [2 + 2]-cycloaddition of alkenes and alkynes utilizing an iron complex as a catalyst was reported by Rosenblum and Scheck [48]. The application of the [CpFe(CO)2]BF4 complex (Scheme 9.21) gave the desired cyclobutene derivatives 29 in up to 53% yield. 

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