Porphyrins iron complex

Fig. 2. Structure of some porphyrin-iron complexes. Protoheme IX (Proto) R = —CH=CH2 Deuteroheme IX (Deut) R = —H Mesoheme IX (Meso) R =...

Iron porphines constitute the active site of hemoproteins and as such are among the most important and most widely studied series of metal complexes. The syntheses of iron protoporphyrin (heme) and its derivatives are important for the reconstitution of hemoproteins (particularly when one wishes to incorporate 57Fe for Mossbauer studies), as well as for model studies. In addition to the naturally occurring porphyrins, iron complexes of both 5,10,15,20-tetraphenyl-21//,23//-porphine (H2tpp) and octaethyl-21//,23//-porphine (H2oep) are widely used in model studies of the natural systems. 

Oxidations. By using Phl=0 (in presence of KBr) as an oxidant, alcohols are oxidized to acids and ketones in water in excellent yields. When catalyzed by either poly(4-vinylpyridine)-supported sodium ruthenate or a (salen)chromium complex chemoselective oxidation of alcohols (e.g., allylic alcohols to alkenoic acids) occurs, which is contrary to the effect of (salen)manganese and (porphyrin)iron complexes (giving epoxy alcohols). ... 

Cytochromes are porphyrin iron complexes bound to proteins which, as enzymes, play an important role in the oxidative phosphorylation in the respiratory cycle. 

NON-PORPHYRIN IRON COMPLEX-CATALYZED EPOXIDATION OF OLEFINS... 

It has been widely accepted that the high-valent iron oxo complex 1 is the active oxidant in metalloporphyrin systems and in non-porphyrin iron complex systems as well. A high-valent iron oxo species can be formed via heterolytic 0-0 bond cleavage of the iron-hydroperoxide 2 or of the iron-peroxyacid species 4 (Figure 5, pathway A). Recently, elegant proof of this heterolytic 0-0 bond cleavage of hydrogen peroxide, MCPBA, and f-butyl hydroperoxide has been provided by Traylor et al in iron porphyrin... 

The hemoglobin molecule is a tetramer composed of two similar globins (polypeptide chain) of unequal length. In the center of the protein lies a prosthetic group made of a porphyrin nucleus. This acts as a tetradentate ligand for the iron ion. The porphyrin-iron complex is called a heme group. The association of a protein molecule with a heme is referred to as a hemo-protein. 

Porphyrin, tetrahydro-metal complexes geochemistry. 6, 862 Porphyrin, tetraphenyl-indium complexes radiopharmacology, 6, 971 iron complexes, 4, 260,1266 zinc complexes spectra, 6, 617... 

One-electron oxidation of the vinylidene complex transforms it from an Fe=C axially symmetric Fe(ll) carbene to an Fe(lll) complex where the vinylidene carbon bridges between iron and a pyrrole nitrogen. Cobalt and nickel porphyrin carbene complexes adopt this latter structure, with the carbene fragment formally inserted into the metal-nitrogen bond. The difference between the two types of metalloporphyrin carbene, and the conversion of one type to the other by oxidation in the case of iron, has been considered in a theoretical study. The comparison is especially interesting for the iron(ll) and cobalt(lll) carbene complexes Fe(Por)CR2 and Co(Por)(CR2) which both contain metal centers yet adopt... 

Six-coordinate organoiron porphyrin nitrosyl complexes, Fe(Por)(R)(NO), were prepared from Fe(Por)R (Por = OEP or TPP R = Me, n-Bu, aryl) with NO gas. The NMR chemical shifts were typical of diamagnetic complexes, and the oxidation state of iron was assigned as iron(ll). ... 

The photochemistry of several of the iron porphyrin halocarbene complexes Fe(TPP)(=CXY) (CXY = CCF, CBr2, CCIF. CCl(CN) and the vinylidene complex Fe(TPP)=C=CAr2 (Ar = p-C6Fl4Cl) has been studied in degassed benzene... 

Diazoalkanes are u.seful is precursors to ruthenium and osmium alkylidene porphyrin complexes, and have also been investigated in iron porphyrin chemistry. In an attempt to prepare iron porphyrin carbene complexes containing an oxygen atom on the /(-carbon atom of the carbene, the reaction of the diazoketone PhC(0)C(Ni)CH3 with Fe(TpCIPP) was undertaken. A low spin, diamagnetic carbene complex formulated as Fe(TpCIPP)(=C(CH3)C(0)Ph) was identified by U V-visible and fI NMR spectroscopy and elemental analysis. Addition of CF3CO2H to this rapidly produced the protonated N-alkyl porphyrin, and Bit oxidation in the presence of sodium dithionitc gave the iron(II) N-alkyl porphyrin, both reactions evidence for Fe-to-N migration processes. ... 

The isocyanide ligand, CNR, is formally isolobal with a carbene ligand. Several studies have investigated iron(Ill) porphyrin isocyanide complexes which have the general formula [FeCPorKCNR) ]. However, these studies have mostly been concerned with spin state and spectroscopic properties rather than chemical transformations and will not be discussed in detail here. Crystallographic details are given for two of the complexes. " ... 

In addition to nonheme iron complexes also heme systems are able to catalyze the oxidation of benzene. For example, porphyrin-like phthalocyanine structures were employed to benzene oxidation (see also alkane hydroxylation) [129], Mechanistic investigations of this t3 pe of reactions were carried out amongst others by Nam and coworkers resulting in similar conclusions like in the nonheme case [130], More recently, Sorokin reported a remarkable biological aromatic oxidation, which occurred via formation of benzene oxide and involves an NIH shift. Here, phenol is obtained with a TON of 11 at r.t. with 0.24 mol% of the catalyst. 

Scheme 1 Schematic structures of iron meio-tetraarylporphyrins and preparation of Fe-porphyrin carbene complexes...

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