Iron alkoxide

The acetylacetonates are stable in air and readily soluble in organic solvents. From this standpoint, they have the advantage over the alkyls and other alkoxides, which, with the exception of the iron alkoxides, are not as easily soluble. They can be readily synthesized in the laboratory. Many are used extensively as catalysts and are readily available. They are also used in CVD in the deposition of metals such as iridium, scandium and rhenium and of compounds, such as the yttrium-barium-copper oxide complexes, used as superconductors. 1 1 PI Commercially available acetyl-acetonates are shown in Table 4.2. 

The tetranuclear iron alkoxide halides (see Table 12.23) were supposed to possess the cubane-like or Ti4(OMe)i4 type structures. The Mossbauer spectroscopy indicated the presence of 2 types of iron atom coordination in Fe4Hal6(OMe)6 4MeOH and only one kind of octahedral arrangement in FeCl(OR)2 and Fe4Hal3(OMe)9. For the 2 latter products the layered structures of the Al(OH)3 type were also proposed [867, 1065]. 

Alkoxides of late transition metals are not easily available. Some chemical companies produce alkoxides of late transition metals, but they are expensive and too reactive to infiltrate into the template. They react quickly on the surface of the template, and solids that are produced prevent complete infiltration. An example using iron alkoxide, Fe(OEt)3, has been reported, but in this case, some nonporous bulk material existed in the sample. 

Kimata M, Nakagawa D, Hasegawa M (2003) Preparation of monodisperse magnetic particles by hydrolysis of iron alkoxide. Powder Technol 132 112-118... 

L2Fe(OCHC6H5)2 (L stands for A7, A7 -bis(trimethylsilyl)benzamidinate) (Fig. 15) is also an effective initiator. The polydispersity of poly(e-CL) and poly(LA) is however rather high (1.5 < M IM < 1.9), and the order in iron alkoxide is fractional (0.5), which points to an aggregation phenomenon. In this case, the bulky ligand makes the kinetics more complex and 50 times slower (86). 

Sol-gel synthesis presents a soft route to materials preparation, where a sol is obtained from the hydrolysis and condensation of a precursor which can form a gel before subsequent drying and heat treatment allows for conversion to a desired phase. An example of a modified sol-gel approach is the preparation of an iron oxide-silica nanocomposite. Here, the iron alkoxide precursor [Fe(OBu )2(THF)]2 has been hydrolysed using millipore water under ultrasonic irradiation in the presence of tetraethylorthosilicate (TEOS) to afford a nanocomposite comprised of silica and y-Fe203 nanoparticles in a single step. The concentration of TEOS added also affects the particle shape, with roughly spherical particles formed with lower and nanorods at higher concentrations, respectively. 

Iron(III) hydroxide [1309-33-7], FeH02, is a red-brown amorphous material that forms when a strong base is added to a solution of an iron(III) salt. It is also known as hydrated iron(III) oxide. The fully hydrated Fe(OH)3 has not been isolated. The density of the material varies between 3.4-3.9 g/cm, depending on its extent of hydration. It is insoluble in water and alcohol, but redissolves in acid. Iron(III) hydroxide loses water to form Fe203. Iron(III) hydroxide is used as an absorbent in chemical processes, as a pigment, and in abrasives. Salt-free iron(III) hydroxide can be obtained by hydrolysis of iron(III) alkoxides. 

Hydroxy-substituted iron-acyl complexes 1, which are derived from aldol reactions of iron-acyl enolates with carbonyl compounds, are readily converted to the corresponding /i-methoxy or /1-acetoxy complexes 2 on deprotonation and reaction of the resulting alkoxide with iodomethane or acetic anhydride (Tabic 1). Further exposure of these materials to base promotes elimination of methoxide or acetate to provide the a,/ -unsaturated complexes (E)-3 and (Z)-3 (Table 2). 

Low activity has been reported for several simple iron-based initiators including oxides,827 porphyrins,860 carboxylates861-863 and alkoxides, 64-866 However, the ferric cluster [Feslqs-0)(OEt)13], (284), is a highly active initiator for the polymerization of LA 867 97% conversion of 450 equivalents is achieved in just 21 min at 70 °C in toluene. Polydispersities are typically between 1.15 and 1.30, even at monomer loadings of 1,000 equivalents. 

Iron, Fe2+ (d6) Iron, Fe2+ (d6) 4, tetrahedral 6, octahedral N-Thiolate O-Carboxylate, alkoxide, oxide, phenolate Electron transfer, nitrogen fixation in nitrogenases, electron transfer in oxidases... 

Alkoxide gels, 23 60 Alkoxide gels, in optical fiber manufacturing, 11 145 Alkoxide initiators, 14 259 Alkoxide ligands, thorium, 24 770 Alkoxides, 12 190 25 72-86 controlled hydrolysis of, 23 56 iron, 14 533 mixed-metal, 25 100 titanium, 25 82 uranium complexation with,... 

Iron-air cells, 3 515-516 Iron(III) alkoxides, 74 533 Iron alloys, 74 490... 

Fig. 3.11. Generation of cationic iron alkylidene complexes by acid-catalyzed a-abstraction of alkoxide [441,447],...

Acid-catalyzed dealkoxylation is particularly suitable for the preparation of highly reactive, cationic iron(IV) carbene complexes, which can be used for the cyclopropanation of alkenes [438] (Figure 3.11). Several reagents can be used to catalyze alkoxide abstraction these include tetrafluoroboric acid [457-459], trifluoroacetic acid [443,460], gaseous hydrogen chloride [452,461], trityl salts [434], or trimethylsilyl triflate [24,104,434,441,442,460], In the case of oxidizing acids (e.g. trityl salts) hydride abstraction can compete efficiently with alkoxide abstraction and lead to the formation of alkoxycarbene complexes [178,462] (see Section 2.1.7). 

Fig. 4. The structure of the cation of 4B, [Fe402(BICOH)2(BICO)2 (02CPh)4]showing the 40% probability thermal ellipsoids. Only the first atom of the phenyl rings is shown. BICOH stands for bis(N-methylimldazol-2-yl)carbinol. BICO is the alkoxide anion, (a) The Fe402 core iron coordination spheres and bridging benzoate groups. Continued on next page.

Some reactions of 2,2 -bipyridine /V-oxides have been reported. The l,T-dioxide is nitrated readily to 4,4 -dinitro-2,2 -bipyridine 1,T-dioxide. ° ° °" 2,2 -Bipyridine 1-oxide is also nitrated in the 4 position. The nitro groups in 4,4 -dinitro-2,2 -bipyridine l,T-dioxide are reactive, being replaced by chlorine with concentrated hydrochloric acid," by bromine with acetyl bromide, by hydroxyl with dilute sulfuric acid, and by alkoxy groups with sodium alkoxides. Some of the dialkoxy derivatives are useful catalysts for the oxidation of aromatic compounds. The dinitro dioxide is deoxygenated to 4,4 -dinitro-2,2 -bipyridine with phosphorus trichloride in chloroform, and other substituted l,T-dioxides behave similarly, but with phosphorus trichloride alone, 4,4 -dichloro-2,2 -bipyridine results. The dinitro dioxide is reduced by iron powder in acetic acid to 4,4 -diamino-2,2 -bipyridine, whereas 4,4 -dichloro-2,2 -bipyridine l,T-dioxide is converted to its 4,4 -diamino analogs with amines. Related reactions have been described. ... 

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