Iron-oxalato-complexes

Iron, tris(hexafluoroacetylacetone)-structure, 1,65 Iron, tris(oxalato)-chemical actinometer, 1,409 photoreduction, 1,471 relief-image-forming systems, 6,125 Iron, tris(l,10-phenanthroline)-absorptiometry, 1,549 racemization, 1,466 solid state, 1,467 structure, 1, 64 lron(III) chloride amino acid formation prebiotic systems, 6,871 Iron complexes acetonitrile. 4,1210 acetylacetone, 2,371 amidines... 

Table 10.2 Quantum yield, of dissolved iron(II) formation under the assumption that the iron(lll) oxalato surface complex is the chromophore.

Also, photolysis of dissolved iron(III) oxalato complexes, which are photolyzed with high quantum yields, has to be taken into account in order to describe this... 

Zuo, Y., and J. Hoigne, Formation of Hydrogen Peroxide and Depletion of Oxalic Acid in Atmospheric Water by Photolysis of Iron(III)-Oxalato Complexes, Environ. Sci. Technoi, 26, 1014-1022 (1992). 

Zuo, Y. and Hoignd, J. (1992) Formation of hydrogen peroxide and depletion of oxalic acid in atmospheric water by photolysis of iron(III)-oxalato complexes. Environ. Sci. Technol. 26, 1014-1022. 

Figure 5. Qualitative representation of the energetics of the photochemical reductive dissolution of lepidocrocite with oxalate as the electron donor. >Fe uOx is the iron(III) oxalato surface complex (i.e., the precursor complex) in its electronically ground state and >FeOx is the precursor complex in its electronically excited state. AG is the free energy of the overall reductive dissolution process AGE7/ is the free energy of activation of formation of a reduced surface iron, >Fe(Il), and the oxidized oxalate, C204 and AGDE1 is the free energy of activation of detachment of the reduced surface iron from the crystal lattice. For the sake of simplicity, the oxidized product is omitted in this figure. (Adapted from reference 9. Copyright 1991 American Chemical Society.)...

We have chosen hematite oxalate as a model system, since the photochemical properties of colloidal hematite (Stramel and Thomas, 1986) and the photochemistry of iron(III) oxalato complexes in solution (Parker and Hatchard, 1959) have been studied extensively. The experiments presented in this section were carried out as batch experiments with monodispersed suspensions of hematite (diameter of the particles 50 and 100 nm), synthesized according to Penners and Koopal (1986) and checked by electron microscopy and X-ray diffraction. An experimental technique developed for the study of photoredox reactions with colloidal systems (Sulzberger, 1983) has been used. A pH of 3 was chosen to maximize the adsorption of oxalate at the hematite surface. This case study is described in detail by Siffert (1989) and Siffert et al. (manuscript in preparation). 

Platinates, bis(oxalato)-, 139 cadmium complexes superstructure, 142 cobalt complexes, 140 electrical conductivity, 14] superstructure, 141 thermopower, 141 divalent cation salts, 140 iron complexes structure, 142 lead complexes superstructure, 142 magnesium complexes, 140 electrical conduction, 142 structure, 142 thermopower, 142 modulated superstructure, 139 monovalent cation salts, 139 nickel complexes structure, 141 partially oxidized, 139 Platinates, tetracyano-, 136 anion-deficient salts, 136 electrical conduction, 138 optical properties, 138 cation-deficient salts, 138 oxidation states, 136 partially oxidized, 138 semiconductors, 134 Platinum colloidal... 

The first structure of a three-dimensional transition metal network incorporating the oxalate ion was that of [Ni(phen)3][KCo (ox)3] 2H20 (phen= 1,10-phenanthroline) reported by Snow and co-workers in 1971. The true dimensionality of this compound, however, went unrecognized during this period, and the potential of oxalate ions to form three-dimensional networks was not fully realized until 1993, when Decurtins et al. published the crystal structure of the iron(II)-oxalato complex with tris(2,2 -bipyridine)iron(II) cations. This compound has an overall stoichiometry of [Fe (bipy)3] [Fe 2(ox)3] " and forms a three-dimensional anionic polymeric network that is best described with the three-connected decagon network topology. A view of this anionic network is shown in Figure 43. 

Figure 9 illustrates the complicated interacticMis of iron-oxalato complex photochemistry with radical chemistry and the chemistry of organic substances. The main impacts of iron complex photochemistry are ultimately (1) breaking of C-C bonds and thus degradation of the hgand (oxalate) and (2) formation of radicals... 

Photolysis of triarylsilyl chromates in the presence of PBN gives triarylsilyl adducts by way of what was considered to be the first example of the transformation of Cr(VI) into Cr(V) (Rehorek et al., 1978). Photolysis of a tris(oxalato)iron(III) complex with PBN gives species considered to be the adducts of (C02)2 and C02 (Rehorek et al., 1977). 

After the resolution of 1-2-chloro-ammino-diethylenediamino-cobaltie chloride many analogous resolutions of optically active compounds of octahedral symmetry were carried out, and active isomers of substances containing central cobalt, chromium, platinum, rhodium, iron atoms are known. The asymmetry is not confined to ammines alone, but is found in salts of complex type for example, potassium tri-oxalato-chromium, [Cr(Ca04)3]K3, exists in two optically active forms. These forms were separated by Werner2 by means of the base strychnine. More than forty series of compounds possessing octahedral symmetry have been proved to exist in optically active forms, so that the spatial configuration for co-ordination number six is firmly established. 

Iron(III) complex compounds, anions, oxalato, K2[Fe(C204)a]-3H20, 1 36... 

There are also carboxylates15 (Section 17-E-10), phosphates, catecholates, and oxalates. Most of the divalent iron oxalato compounds have a chain structure but the product of photoreduction of mononuclear [bipyH] [Feni(ojc)2(H20)2] gives a three-dimensional anionic polymeric network of [Fe2I(ox)3]2 1 and [Fen(bipy)3]2+ ions.16 Magnetic exchange typically occurs through the oxalate bridges.17 Six-coordinate iron(II) a-amino acid complexes are readily obtained from the reaction of the 4-coordinate Fe(mes)2(phen) and the protic amino add, AH, in THF 18... 

---