Selenium organometallic compounds

It is now well established that organometallic compounds are formed in the environment from mercury, arsenic, selenium, tellurium and tin and hence were also deduced on the basis of analytical evidence for lead, germanium, antimony and thallium. Biological methylation of tin has been demonstrated by the use of experimental organisms. Methylgermanium and methyllead were widely found in the environment but it is debatable whether germanium and lead are directly methylated by biological activity in natural environment. 

Gas chromatography and mass spectroscopy (GC/MS) of inorganic and organometallic compounds, 18 273-276 Gaseous hydroxides, 5 215-258 dimerization of, 5 224 mass spectrometric study of, 5 220-225 metalic, 5 220 nonmetallic, 5 217-220 study of in oxyhydrogen flame, 5 225-226 types of, 5 215-217 Gases, see also specific substances high ternperamre species from, 14 137-139 thermal decomposition of, 17 90-93 Gas phase electron resonance spectra, of sulfur and selenium fluorides, 24 190... 

Since dioxiranes are electrophilic oxidants, heteroatom functionalities with lone pair electrons are among the most reactive substrates towards oxidation. Among such nucleophilic heteroatom-type substrates, those that contain a nitrogen, sulfur or phosphorus atom, or a C=X functionality (where X is N or S), have been most extensively employed, mainly in view of the usefulness of the resulting oxidation products. Some less studied heteroatoms include oxygen, selenium, halogen and the metal centers in organometallic compounds. These transformations are summarized in Scheme 10. We shall present the substrate classes separately, since the heteroatom oxidation is quite substrate-dependent. 

C.R. Johnson, Sulfoximides, in D. Barton u. W.D. Ollis, Comprehensive Organic Chemistry, Bd. 3, D.N. Jones, Sulphur, Selenium, Silicon, Boron, Organometallic Compounds, S. 223, Pergamon Press, Oxford New York Toronto Sydney Paris - Frankfurt 1979. 

Jones, Sulphur, Selenium, Silicon, Boron, Organometallic Compounds, S. 237, Pergamon Press, Oxford New York Toronto. Sydney Paris Frankfurt 1979. 

The reaction of bis-phenylpropargyl ether (321) with tris(triphenylphosphine)rhodium chloride in benzene or toluene led to the formation of the unusual organometallic compound (322), which can be viewed as a derivative of an oxygen-rhodium pentalene system. Reaction of the rhodium complex (322) with sulfur leads to the corresponding 4,6-diphenyl-l,3-dihydro[3,4-c]furan (323). The selenium and tellurium analogs (324) and (325) were made in a similar manner (Scheme 111) (76LA1448). 

Capillary electrophoresis (CE) provides high resolution for separation of chemical compounds. Separations of metal ions, of metal ions in different oxidation states and of organometallic compounds are all possible with appropriate CE conditions. This technique is being investigated for speciation. Since sample volumes in CE are generally very small, a detector capable of very low detection limits is desirable. Thus, ICP-MS has been combined with CE to provide a means for studying metal speciation. CE-ICP-MS procedures have been described for the separations of platinum species (Michalke and Schramel, 1996), selenium species (Kumar et al., 1995 Michalke and Schramel, 1996) and arsenic species (Magnuson et al., 1997). Detection limits were about 1 mgl 1 (platinum species) and 10 and 24 pg for Sclv and Scvl, respectively. An application of CE-ICP-MS to platinum species in soils is described in Section 15.8.6. 

Klayman, D. L. Gunther, W. H. H. The Chemistry of Organometallic Compounds, a Series of Monographs Organic Selenium Compounds, Wiley New York, 1973. 

The reaction of a polar organometallic compound with elemental sulfur, selenium or tellurium gives a thiolate, selenolate or tellurolate, respectively [60, 61] in many syntheses, however, further reactions are carried out with the intermediary chalcogenates , e.g. alkylations ... 

Many analytes may form volatile species with other elements in the sample, for example, halides, or be present in compounds that exhibit high-vapor pressures at relatively low temperatures (mercury, arsenic, selenium, organometallics). Such compounds may be volatilized and swept from the tube, in molecular form, prior to the atomization step. These losses can be dealt with by adding a large excess of a reagent (a modifier) to change, in situ, the thermochemical behavior of the analyte and the matrix. 

Organometallic compounds are those in which there is a metal-carbon bond. According to this definition, in the case of transition metals, this group of compounds includes not only metal carbonyls, olefin complexes, cyclopentadienyl, and other 7r-complexes, but also cyanide and fulminate compounds. Certain difficulties arise in defining the metal of the main group elements. Usually, organometallic compounds are comprised not only of compounds of typical metals, but also of metalloids such as boron, silicon, phosphorus, arsenic, selenium, etc. In compounds of metals as well as in those of metalloids, the bond is generally polarized as follows C. Consequently, the... 

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