Coordination of iron

To mimic the square-pyramidal coordination of iron bleomycin, a series of iron (Il)complexes with pyridine-containing macrocycles 4 was synthesized and used for the epoxidation of alkenes with H2O2 (Scheme 4) [35]. These macrocycles bear an aminopropyl pendant arm and in presence of poorly coordinating acids like triflic acid a reversible dissociation of the arm is possible and the catalytic active species is formed. These complexes perform well in alkene epoxidations (66-89% yield with 90-98% selectivity in 5 min at room temperature). Furthermore, recyclable terpyridines 5 lead to highly active Fe -complexes, which show good to excellent results (up to 96% yield) for the epoxidation with oxone at room temperature (Scheme 4) [36]. 

Coordination of iron in oxy- (low-spin) and deoxy- (high-spin) hemoglobin... 

The known Fe(OAlk)2 are green polymeric substances. The diffuse reflectance spectrum of Fe(OMe)2 indicates the octahedral coordination of iron atoms [6], According to the X-ray powder data its structure is isomorphous to those of other divalent metals, — i.e., resembles that of Fe(OH)2 (Mg(OH)2 type) [1656], The solubility is characteristic only of the derivatives of rather branched radicals — CH2Ph, CPh3 [114,941] — or of the phenoxides solvated by such bulky ligand as Dipy [941], The octahedral coordination is observed not only for the methoxide but quite unexpectedly for the derivatives 3,5-sus-... 

Protection and Activation of Alkenes by the Coordination of Iron Carbonyls... 

The Mossbauer spectra of iron in numerous minerals have been studied, but a few examples will serve to illustrate this technique. In the rockforming silicate minerals, Mdssbauer spectroscopy has been used to study the oxidation state, spin state and coordination of iron, and its distribution between different sites in a structure. Thus, Fig. 2.46 (after Williams et al., 1971) shows the spectrum of an augite [essentially (Ca,Mg,Fe)2Si20J, the structure of which contains two kinds of sixfold-coordinate sites that may be occupied by iron (the Ml and M2 sites). The Mdssbauer spectrum can be fitted to three quadrupole doublets peaks 1 and 1 have parameter characteristic of Fe (in both Ml and M2 sites), peaks A and A have parameters characteristic of Fe in Ml, and peaks C and C of Fe + in the M2 sites. These assignments, based chiefly on comparisons with endmember compositions and related species, also enable estimates of site populations to be made on the basis of the areas under the peaks. Studies of the variation in site populations as a function of composition and thermal treatment have led to important advances in understanding intercrystalline order-disorder equilibria, as pioneered in the work of Virgo and Hafner (1970). 

The structure of [Fe4Te2(CO)i4] is shown in Fig. 20. The central Fe2Te2(CO)6 fragment does not have the ideal butterfly-type structure due to a shift from the square-pyramidal towards a predominantly trigonal-bipyraraidal coordination of iron. 

The four Fe(CO)4 fragments of [Fe4Te(CO)i6] are bonded to a central telluride ion in a tetrahedral fashion. The resulting coordination of iron is trigonal-bipyramidal with tellurium defining a common axial position for each FeTe(CO)4 fragment. 

CaO —FeO... A slight shift of the iron atoms in the FeO layers leads to a tetrahedral coordination of iron in this layer resulting in alternate sheets of FeOg octahedra and FeOa tetrahedra (OTOT. ) in the c-direction (Fig. 6b). We have recently prepared a new oxide, Ca2FeCoOs, possessing the brownmillerite structure wherein Fe and Co occupy tetrahedral and octahedral sites respectively. 

Distribution of Fe and Fe framework ions and their coordinations in FeAPO-11 structure were investigated employing Mossbauer spectroscopy and X-ray powder diffraction. Simultaneous stabilization of Fe " and Fe ions in various coordination states was observed. It was shown that the structure of FeAPO-11 is rather flexible and the coordination of iron strongly depends on the form of pretreatment. Among ferrous ions, facile transition between octahedral and distorted trigonal coordinations was observed. 

Lewandowska H, Stepkowski TM et al (2012) Coordination of iron ions in the form of histidinyl dirritrosyl complexes does not prevent their genotoxicity. Bioorg Med Chem 20 6732-6738... 

Keyes, W. E., T. M. Loehr, and M. L. Taylor Raman Spectral Evidence for Tyrosine Coordination of Iron in Protocatechuate 3,4-Dioxygenase. Biochem. Biophys. Res. Commun. 83, 941 (1978). 

ESI Mechanistic study of coordination of iron(lll) cations to -keto esters Trageeta/. [285]... 

Trage, C., Schroder, D., Schwarz, H. (2005) Coordination of Iron(III) Cations to fi-Keto Esters as Studied by Electrospray Mass Spectrometry Implications for Iron-catalyzed Michael Addition Reactions. Chem. Eur. J. 11 619-627. 

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