Bioorganometallic Chemistry of Ferrocene

High-resolution Fe K-edge XANES spectra of a series of crystalline Fe 2+ - and Fe 3+ -bearing model compounds were measured in an effort to correlate characteristics of the pre-edge feature with oxidation state and local coordination environment of Fe atoms. The model compounds comprise 30 natural minerals and synthetic compounds, with Fe coordination environments ranging from 4 to 12 O atoms for Fe 2+ , including 5-coordinated trigonal bipyramidal Fe 2+ , and from 4 to 6 O atoms for Fe 3+ . Most pre-edge spectra show two components (due to crystal-field splitting) that are located just above the Fermi level. The most useful characteristics of the Fe-K pre-edge for determining Fe oxidation state and coordination number are the position of its centroid and its integrated intensity. The separation between the average pre-edge centroid positions for Fe 2+ and Fe 3+ is 1.4 ± 0.1 eV. Thus, the position of the pre-edge feature can be used as a measure of the average Fe-redox state, with the average pre-edge position for mixed Fe 2+ -Fe 3+ compounds occurring between positions for Fe 2+ and Fe 3+ . The lowest pre-edge normalized heights and integrated intensities are observed for the most centrosymmetric sites of Fe, in agreement with previous studies (see Waychunas et al. 1983). Examination of the pre-edge features of mechanical mixtures of phases containing different proportions of Fe 2+ and Fe 3+ suggests that the pre-edge position and intensity for these mixtures can vary quite non-linearly with the average redox state of Fe. However, distinctly different trends of pre-edge position vs. pre-edge intensity can be observed, depending on the coordination environment of Fe 2+ and Fe 3+ , with an accuracy in redox determination of ±10 mol% provided that the site geometry for each redox state is known. These methods have been used to estimate the Fe 3+ /Fe 2+ ratio in 12 minerals (magnetite, vesuvianite, franklinite, rhodonite, etc.) containing variable/unknown amounts of Fe 2+ /Fe 3+ .

http://www.minsocam.org/msa/ammin/toc/Abstracts/2001_Abstracts/MJ01_Abstracts/Wilke_p714_01.pdf

Oxidation state and coordination of Fe in minerals: An Fe K-XANES spectroscopic study

mproved activity–composition relationships for biotite, garnet and silicate liquid are used to construct updated P–T grids and pseudosections for high-grade metapelites. The biotite model involves Ti charge-balanced by hydrogen deprotonation on the hydroxyl site, following the substitution , where HD represents the hydroxyl site. Relative to equivalent biotite-breakdown melting reactions in P–T grids in K2O–FeO–MgO–Al2O3–SiO2–H2O (KFMASH), those in K2O–FeO–MgO–Al2O3–SiO2–H2O–TiO2–O2 (KFMASHTO) occur at temperatures close to 50 °C higher. A further consequence of the updated activity models is that spinel-bearing equilibria occur to higher temperature and higher pressure. In contrast, the addition of Na2O and CaO to KFMASH to make the Na2O–CaO–K2O–FeO–MgO–Al2O3–SiO2–H2O (NCKFMASH) system lowers key biotite-breakdown melting reactions in P–T space relative to KFMASH. Combination of the KFMASHTO and NCKFMASH systems to make Na2O–CaO–K2O–FeO–MgO–Al2O3–SiO2–H2O–TiO2–O2 (NCKFMASHTO) results in key biotite-breakdown melting reactions occurring at temperatures intermediate between those in KFMASHTO and those in NCKFMASH. Given such differences, the choice of model system will be critical to inferred P–T conditions in the application of mineral equilibria modelling to rocks. Further, pseudosections constructed in KFMASH, NCKFMASH and NCKFMASHTO for several representative rock compositions show substantial differences not only in the P–T conditions of key metamorphic assemblages but also overall topology, with the calculations in NCKFMASHTO more reliably reflecting equilibria in rocks. Application of mineral equilibria modelling to rocks should be undertaken in the most comprehensive system possible, if reliable quantitative P–T information is to be derived.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1525-1314.2007.00711.x

Progress relating to calculation of partial melting equilibria for metapelites

The challenge of cyclic and acyclic schiff bases and related derivatives

Non-platinum chemotherapeutic metallopharmaceuticals.

Influence of firing conditions on ceramic products: Experimental study on clay rich in organic matter

Here we describe the evolution of iron-bearing phases in the firing of carbonate-rich illite and chlorite clay. Breakdown of chlorite forms an amorphous phase, which continues to retain iron in a (distorted) paramagnetic octahedral site, until carbonates start to decompose and react at 750 °C, forming Ca-silicates. Only at this temperature can hematite nucleate and grow in specific micro-domains located in former chlorite flakes. At 950 °C, decomposition of illite in the presence of an amorphous phase and CaO produces a melt in which nano-sized hematite may nucleate, although its growth is inhibited due to low diffusion with respect to soaking time.

Hematite nucleation and growth in the firing of carbonate-rich clay for pottery production

Heteropolymetallic complexes of 1,1′-Bis(diphenylphosphino)ferrocene (dppf). III. Comparative physicochemical properties of (dppf)MCl2 (M = Co, Ni, Pd, Pt, Zn, Cd, Hg)

Eight tris(organotin)-substituted Keggin tungstosilicate heteropolyanions have been synthesized and characterized by elemental analysis, infrared and Mossbauer spectroscopy, multinuclear NMR, and X-ray crystallography. The new anions contain alpha- or beta-SiW(9)O(34)(10)(-) moieties and are of two structural types, [(RSn)(3)(SiW(9)O(37))](7)(-) (R, isomer: Ph, alpha-, 1; n-Bu, alpha-, 2; Ph, beta-, 3; n-Bu, beta-, 4) and [(RSnOH)(3)(SiW(9)O(34))(2)](14)(-) (Ph, alpha-, 5; n-Bu, alpha-, 6; Ph, beta-, 7; n-Bu, beta-, 8). Crystals of Cs(4)H(3)[(PhSn)(3)(SiW(9)O(37))].8H(2)O (anion 3) are monoclinic, space group C2/c, with lattice constants a = 48.91(2) A, b = 12.111(3) A, c = 20.334(9) A, beta = 102.30 degrees, and Z = 8. The anion has nominal C(3)(v)() symmetry and has a structure with three corner-shared WO(6) octahedra of the beta-Keggin anion replaced by three PhSnO(5) groups. Crystals of Cs(9)H(5)[(BuSnOH)(3)(SiW(9)O(34))(2)].36H(2)O (anion 6) are tetragonal, space group Pf2(1)m, with lattice constants a = b = 29.005(4) A, c = 13.412(4) A, and Z = 4. The anion has the anticipated D(3)(h)() symmetry and contains three BuSnOH groups sandwiched between A,alpha-SiW(9)O(34)(10)(-) anions.

Polyoxometalate Derivatives with Multiple Organic Groups. 2. Synthesis and Structures of Tris(organotin) Α, Β-Keggin Tungstosilicates

Metal complexes of formula M 2 (CTH) 2 (DHBQ)Y 2 (M=Mn, Fe, Ni; CTH=dl-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane; Y=ClO 4 , PF 6 ) have been obtained by reaction of the appropriate M(CHT) 2+ cation and 2,5-dihydroxy-1,4-benzoquinone (H 2 DHBQ) in alkaline medium. The coupling between the metal ions is weakly antiferromagnetic. On the basis of IR, electronic, EPR, and Mossbauer spectra, evidence is found that these compounds contain the radical species DHBQ 3− bridging the tripositive metal ions

Umberto Russo

Papers

Influence of firing conditions on ceramic products: Experimental study on clay rich in organic matter

Hematite nucleation and growth in the firing of carbonate-rich clay for pottery production

Heteropolymetallic complexes of 1,1′-Bis(diphenylphosphino)ferrocene (dppf). III. Comparative physicochemical properties of (dppf)MCl2 (M = Co, Ni, Pd, Pt, Zn, Cd, Hg)

Polyoxometalate Derivatives with Multiple Organic Groups. 2. Synthesis and Structures of Tris(organotin) Α, Β-Keggin Tungstosilicates

Tetraoxolene radical stabilization by the interaction with transition-metal ions