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Fe III Compounds

Abstract In this chapter, selected results obtained so far on Fe(III) spin crossover compounds are summarized and discussed. Fe(III) spin transition materials of ligands containing chalcogen donor atoms are considered with emphasis on those of M,f T-disubsti-tuted-dithiocarbamates, Ar,N-disubstituted-XY-carbamates (XY=SO, SSe, SeSe), X-xan-thates (X=0, S), monothio-/J-diketonates and X-semicarbazones (X=S, Se). In addition, attention is directed to Fe(III) spin crossover systems of multidentate Schiff base-type ligands. Examples of spin inter-conversion in Fe(III) compounds induced by light irradiation are given. [Pg.275]

Considerably less research has been directed towards Fe(III) compounds of substituted X-xanthates (X=0, S), as well as of the related dithiophosphates (Fig. 3), which can be thought of as being very closely related to the dithio-carbamates. [Pg.288]

Fe(III) compounds exhibiting spin crossover behaviour, its extent depending on the nature of the substituents R1 and R2 indicated in Fig. 4. [Pg.290]

In the following, various Fe(III) compounds of R-substituted salicylaldehyde thiosemicarbazones will be discussed according to the criteria mentioned above, although it should be pointed out that a comparison of these materials may be rendered less meaningful due to the possible occurrence of different polymorphs. Moreover, upon variation of one substitution parameter, several other structural features may also be changed simultaneously. For instance, a change in outer-sphere cation or the introduction of a substituent at the salicylaldehyde moiety is frequently associated with increased hydration of the Fe(III) material. [Pg.293]

A low spin -dntermediate spin transition has also been found for a unique Fe(III) compound having an octahedral FeN4S2 environment [126]. In this compound the Fe(III) ion is surrounded by the tetradentate N-donating macrocycle AT,N/-dimethyl-2,ll-diaza[3.3](2,6)pyridinophane together with... [Pg.299]

Table 3 Average Fe-donor atom bond lengths for Fe(III) compounds of tetradentate N202-donating Schiff base ligandsa,b,c,d... [Pg.302]

The 57Fe Mossbauer spectra for [FexCo x(acpa)2]BPh4 (x=0.035 and 0.074) show that the transition has been displaced to a higher temperature than that for the pure Fe(III) compound [156]. This may again be related to... [Pg.307]

Dinuclear Fe(III) compounds were also obtained using substituted salten derivatives together with 4,4 -bipyridine as bridging ligand [200]. The 3-OMe-salten tetraphenylborate compound seems to show the onset of spin crossover at about 270 K, the 5-OMe-salten material is probably a purely high spin compound, whereas the 5-Cl-salten derivative exhibits gradual spin crossover behaviour. [Pg.322]

Finally, the electrochemical behaviour of [FeH(N2)(dppe)2]+ (dppe = Ph2PCH2CH2PPh2) and [FeH(N2)(depe)2]+ (depe = Et2PCH2CH2PEt2) has been briefly studied. Both complexes undergo oxidation to the corresponding Fe(III) compounds, which are quite stable.54 Even if... [Pg.475]

One obviously expects that these Fe(III) compounds exhibit a Fe(III)/ Fe(II) reduction. However, since the protein has a total negative charge of-13 at pH 7 (pi 3), a situation which is electrostatically opposite to that of cytochrome c, it is fairly intuitive that the use of a perpendicularly... [Pg.556]

Figure 3.8 Accumulation of amorphous Fe(III) compounds under alternating reduction and oxidation (after Moormann and van Breemen, 1978). Reproduced by permission of IRRI... Figure 3.8 Accumulation of amorphous Fe(III) compounds under alternating reduction and oxidation (after Moormann and van Breemen, 1978). Reproduced by permission of IRRI...
More complex spectra are usually obtained. Quadrupole splitting results in two peaks equal in intensity to a first approximation. The amount of splitting is an important parameter, with larger splits occurring for Fe(II) compounds than for Fe(III) compounds. Hyperfine magnetic splitting results in a symmetrical six-peak spectrum with a variation in position and in spread related to the chemical state of the compound. Many superimposed combinations of these as well as broadened peaks and other perturbations are observed when complex materials are examined. [Pg.196]

From the above it is likely that sulfate is reduced before ferric iron. This is contrary to what one would expect from the thermodynamic properties of Fe(III) compounds and sulfates. This may be caused by... [Pg.311]

Barbier-type reactions of alkyl iodides with ketones can be performed with Sml2 when Fe(III) compounds are used as catalysts [22]. Particularly efficient for the intramolecular reaction of co-iodo ketones such as compound 16 turned out to be Fe(dbm)3 (dbm = l,3-diphenyl-l,3-propanedionato). The latter is an air-stable, THF-soluble, non-hygroscopic complex that can be very easily prepared from... [Pg.219]

Dry air is an inefficient oxidant of sulfide minerals. In the presence of water, however, oxidants (such as O2 and Fe(III) compounds) and strong reductants (such as H2S) are important in determining the stability of... [Pg.97]

Depending on saturation, the H3ASO30 may precipitate as arsenolite (Williams, 2001, 274) or remain dissolved in water. As further discussed in Chapters 2 and 7, chemical oxidants (usually Mn(III or IV) or Fe(III) compounds with 02) and/or microorganisms may eventually transform As(III) into As(V). Studies by Lengke and Tempel (2002) also indicate that the oxidation rates of orpiment tend to increase if pH >8. [Pg.105]

Extensive reductive dissolution of Fe(III) compounds in water would release arsenic that might have sorbed or coprecipitated with the compounds. However, the arsenic may immediately sorb or coprecipitate with any Fe(II) compounds that might form. As discussed throughout this chapter, reductive dissolution is an important and ubiquitous process that controls the mobility of arsenic in many sediments, soils, wetlands, estuaries, seas, groundwaters, and stagnant lakes. [Pg.110]


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Compounds III

Fe compounds

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