Synthetic iron complex

Synthetic iron complexes have provided models for two stages of ferritin iron storage and biomineralization (1) the early stages, when small num-... 

All but two of the known synthetic iron(IV)-oxo compounds are low-spin, 5=1 [202, 240]. The first example of an iron(IV)-oxo model compound with spin 5 = 2 was the quasioctahedral complex [(H20)5Fe =0] (5 = 0.38 mm s, A q = 0.33 mm s ) which was obtained by treating [Fe°(H20)6] with ozone in acidic aqueous solution [204]. The spin state of iron in this type of structure is determined by the energy gap between the d,2 y2 and the d y orbitals [241]. The weak water ligands induce a sufficiently small gap being less than the spin paring energy and stabilizing the HS state (Fig. 8.25, case a). 

Siderophores are iron-complexing compounds of low molecular weight that are synthesized by bacteria and fungi, and serve to deliver iron to the microbes. Because of their exclusive affinity and specificity for Fe3+, natural siderophores and synthetic derivatives have been exploited in the treatment of human iron-overload diseases. The most successfully used example is Desferal , which is the methane sulfonate derivative of iron-free ferrioxamine B, a linear trihydroxamate (Figure 3.2). Ferrioxamine was isolated in 1958 from the culture supernatant of Streptomyces... 

Another recent example of sonochemical substitution is in the preparation of 7r-allyllactone(tricarbonyl)iron complexes, which are useful synthetic intermediates in the synthesis of lactones and lactams (185). Upon... 

The mechanism and synthetic scope of reactions of monohaptopropargyl-iron complexes has been described earlier (see Schemes 30-33 in Section IV,A,2). By using sulfur dioxide and sulfur trioxide as electrophilic reagents, it is possible to synthesize metal-containing heterocycles in the reduced 1,2-oxathiole category (sultines and sultones) (Scheme 119).182-184 An... 

In contrast to the reaction of an i72-CS2-rhodium complex with dimethyl acetylenedicarboxylate which gives rise to a metallocycle,186 the iron complexes 103 are converted by activated acetylenes into air-sensitive carbene complexes 104. Decomposition of the latter in air provides an unusual synthetic route to substituted tetrathiofulvene derivatives (Scheme 121).187... 

Hydroxypyranones and hydroxypyridinones are promising candidates as chelating agents for the treatment of iron overload, since many are readily available, they form stable complexes with Fe, and some are permitted food additives. Hydroxypyridinones are to be preferred to hydroxypyranones as the former form the more stable complexes and are less readily metabolized. An extensive literature on synthetic iron chelators has been built up over the past 20 years -we can cite only a very small proportion here. In the 1980s it was established that hydroxypyridinones, usually in the form of... 

Photolysis of cationic alkoxycarbene iron complexes [193] or alkoxycarbene manganese complexes [194] has been used to replace carbonyl groups by other ligands. The alkylidene ligand can also be transferred from one complex to another by photolysis [195], Transfer of alkylidene ligands occurs particularly easily from diaminocarbene complexes, and has become a powerful synthetic method for the preparation of imidazoline-2-ylidene complexes [155,196]. 

Scheme 4. Synthetic routes to an iron complex containing an acyclic diaminocarbene.

Six years later, we described a considerably improved total synthesis of the carbazomycins A (260) and B (261) using highly efficient synthetic routes to the arylamines 780a and 794 (610). Moreover, this methodology uses air as an oxidant for the construction of the carbazole framework by oxidative coupling of the iron-complexed cation 602 with the arylamines 780a and 794. 

There is a number of synthetic substitutes for natural ferritin and the properties of these have been compared with those of ferritin. The synthetic polysaccharide iron complex (PIC), has a magnetic blocking temperature of 48K (Mohie-Eldin et al. 1994). Iron-dextran complexes are used as a substitute for ferritin in the treatment of anaemia. The iron cores of these complexes consist not of ferrihydrite, but of very poorly crystalline akaganeite with magnetic blocking temperatures of between 150 and 290 K (Muller, 1967 Knight et al. 1999) which were lowered from 55K to 35 and 25K, if prepared in the presence of 0.250 and 0.284 Al/(A1 -i- Fe), respectively (Cheng et al.2001). 

Sokolowska-Gajda, J., Freeman, H.S. and Reife, A. (1994) Synthetic dyes based on environmental considerations 1. Iron complexes for protein and polyamide fibers. Text. Res. f, 64 (7), 388-396. 

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... 

Cyclohexadienylium-tricarbonyliron complexes represent the most versatile iron complexes applied as building blocks in synthetic organic chemistry. Because of their positive charge, a large variety of nucleophiles undergo nucleophilic attack at the... 

Using cationic tricarbonyl(q5-cyclohexadienyl)iron complexes as starting materials, different synthetic routes to a large number of carbazole alkaloids have been developed [51, 58, 67]. The first step is an electrophilic substitution of a substituted arylamine using the cyclohexadienyliron complex and provides the corresponding 5-aryl-substituted cyclohexadiene-iron complexes (Scheme 1.29). 

Two examples of non-heme iron complexes with tetradentate ligands should be presented, illustrating the problems associated with the use of such complexes for synthetic purposes. 

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