Sulfur interaction

Balsenc LR (1980) Sulfur Interaction with Surfaces and Interfaces Studied by Auger Electron Spectrometry. 39 83-114... 

Weaver [40] studied alternate cathode materials at 650 °C, finding several that performed well. Steady-state polarization on Ni, Co and Fe porous electrodes operating as cathodes in a MCFC, with a standard (Li/K)2 C03 tile is shown in Figs. 30-32. Note that the oxidant gas fed to these cathodes is, in normal MCFC operation, the fuel, composed of 32.5% H2, 17.5% COz, 17.5% H20, the balance N2. Polarizations were first taken with this clean gas where the only reaction can be Eq. (35). After steady-state was attained, 0.65% H2S was added and sufficient time allowed for the electrode to convert to the sulfides. After 24 hours, the outlet H2S reached the inlet level and polarizations were measured. Note in Figs. 30-32, that the performance with H2S is significantly improved over the clean gas. (The Ni sample was a commercial (Gould) MCFC electrode the Co and Fe were pressed from powders. Each gas was 8 sq cm in superficial area). The improvement is probably due to a catalytic mechanism involving sulfur interactions with the electrode, as, for Co ... 

Flynn, A., A.W. Franzmann, and P.D. Ameson. 1976. Molybdenum-sulfur interactions in the utilization of marginal dietary copper in Alaskan moose (Alces alces gigas). Pages 115-124 in W.R. Chappell and K.K. Peterson (eds.). Molybdenum in the Environment. Vol. 1. The Biology of Molybdenum. Marcel Dekker, New York. 

There are three possible types of three-electron bonds. Oxidation of a u bond leads to a cation-radical with a, u three-electron bond. This bond contains no antibonding electrons, and the total bond strength exceeds that of a double bond by the energy of half a n bond. Olefins can acquire the 2a—In bond on one-electron oxidation, the bond constructed from the electrons 2a and In. Oxidation of organic disulfides, RSSR, to their cation-radicals (RSSR) yields species in which the unpaired electron from the oxidized sulfur interacts with the unbound p-electron pair of the second sulfur (Glass 1999). This establishes a 2n-In bond on top of the already existing o bond. The overall bond strength of this five-electron (2a—2n-In ) bond also exceeds that of the normal... 

Both stopped-flow and rapid freeze quench kinetic techniques show that the substrate reduces the flavin to its hydroquinone form at a rate faster than catalytic turnover Reoxidation of the flavin hydroquinone by the oxidized Fe4/S4 center leads to formation of a unique spin-coupled species at a rate which appears to be rate limiting in catalysis. Formation of this requires the substrate since dithionite reduction leads to flavin hydroquinone formation and a rhombic ESR spectrum typical of a reduced iron-sulfur protein . The appearance of such a spin-coupled flavin-iron sulfur species suggests the close proximity of the two redox centers and provides a valuable system for the study of flavin-iron sulfur interactions. The publication of further studies of this interesting system is looked forward to with great anticipation. 

The results discussed in Section IV have clearly shown that there is increasing evidence for the importance of Pt-sulfur interactions from a bio(chemical) and medical point of view. Although such interactions are not responsible for the antitumor activity of cis-Pt, they probably contribute to some of the mentioned overall negative effects (inactivation, resistance, and nephrotoxicity). Much more research is needed to study these negative effects in detail. This could ultimately lead to compounds with better antitumor properties and lower side effects. 

In the body, Antabuse inhibits acetaldehyde oxidase, presumably via tbe soft-soft molybdenum-sulfur interaction.84 Any alcohol ingested will be converted to acetaldehyde which, in the absence of a pathwny to destroy it, will build up with severely unpleasant effects, discouraging further consumption. 

It has been suggested that intermolecular copper—sulfur interactions in these complexes are of comparable magnitude to proton—sulfur and proton-metal interactions and should not be regarded as a general feature of the structural characteristics of the Cu(R2Dtc)2 complexes. It should be noted that in the structure of the Cu(PyrrolDtc)2 complex, the crystal packing is domin-... 

Sulfur-Sulfur Interactions in Complexes with Monodentate and Polydentate Ligands 530... 

Another type of redox reaction is the formation of disulfide with a two-electron reduction of the metal center M" (equation 3).115 The disulfide formation may be regarded as a limiting case of the sulfur-sulfur interactions which occur in thiolato complexes. 

Equilibrium data are also available for some Ag1 complexes with alkyl-, alkenyl- and phenyl-thioacetic acids. An important conclusion here is that the strength of the Ag—S bond is mainly determined by its o component.34 In addition, the fact that the cis isomer (1) isomerizes to the trans isomer (2) upon moderate heating suggests that there is no strong metal-to-sulfur -interaction.35 Affinity data for other systems have been compiled by Kuehn and Isied.4... 

In contrast to the transition elements, the main group element dithiocarbamates often have asymmetrical metal-sulfur bonds due to the lack of pn-dnMOs. In theses compounds the metal-sulfur interaction. High oxidation states for these dithiocarbamates are only found when high electron density is brought upon the metal by er-donating groups. For instance, (54) exists whereas (55) does not.73... 

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