Arsenic organometallic compounds

G. O. Doak and L. D. Freedman, Organometallic Compounds of Arsenic, Antimony, and Bismuth,]ohn Wiley Sons, Inc., New York, 1970. 

Mercury, tin, lead, arsenic, and antimony form toxic lipophilic organometallic compounds, which have a potential for bioaccumulation/bioconcentration in food chains. Apart from anthropogenic organometallic compounds, methyl derivatives of mercury and arsenic are biosynthesized from inorganic precursors in the natural environment. 

Craig, PJ. (Eid.) (1986). Organometallic Compounds in the Environment—collection of detailed chapters on the environmental chemistry and hiochemistry of organometallic compounds. Environmental Health Criteria 18 Arsenic Environmental Health Criteria 85 Lead Environmental Aspects Environmental Health Criteria 86 Mercury, Environmental Aspects Environmental Health Criteria 101 Methylmercury Environmental Health Criteria 116 Tributyltin... 

There are many organometallic compounds of arsenic, antimony, and bismuth known that constitute series having chemical properties that differ markedly. These compounds generally decrease in stability in the order As > Sb > Bi, which agrees with the increasing difference in size of the atoms and carbon atoms. Arsenic compounds include both aliphatic derivatives and heterocycles such as arsabenzene,... 

The application of these techniques has led to the discovery of a number of organometallic species of arsenic, tin, and antimony in the marine environment. Germanium has not been observed to form organometallic compounds in nature. Some aspects of the geochemical cycles of these elements which have been elucidated by the use of these methods are discussed. 

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. 

As was the case with the volume The chemistry of organic arsenic, antimony and bismuth compounds, published in 1994, it was clear that the set of five volumes describing organometallic compounds (edited by Professor Frank R. Hartley) did not deal in sufficient depth with organic compounds of germanium, tin and lead. Hence we decided to publish the present volume, which we hope will be a useful and worthwhile addition to the series The Chemistry of Functional Groups. In this volume the authors literature search extended in most cases up to the end of 1994. 

The initial decomposition of Ga(CH3)3 involves the loss of methyl radicals (114-121). These methyl radicals can subsequently react with H2 or the arsenic source, such as AsH3, abstract H from an organometallic or hydrocarbon species, or recombine. The reaction with H2 leads to H radicals that can react with the parent organometallic compound to accelerate its decomposition. The following are some of the reactions ... 

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. 

Classes of organic compounds analysed by this technique include non ionic surfactants, fatty acids, hydrocarbons (all types), organochlorine compounds, organosulphur and phosphorus compounds, substituted aromatic compounds, NT A, EDTA and insecticides and herbicides. Organometallic compounds studied include those of arsenic, lead, germanium, mercury and tin. 

The one exception is the capacity of some micro-organisms to methylate certain metals, e.g. arsenic, antimony and mercury, probably as a kind of detoxification mechanism. Methylcobal-amin is the only organometallic compound known to have a physiological function in life processes. 

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