Organo elemental arsenic

Some oxygen-containing heteroelement compounds, in which other elements are not coordinatively active, could be attributed to O-ligands. This group includes in particular nitrogen, phosphorus, arsenic, and antimony organo-oxides [1,3,11,112], The most studies amongst them are phosphine oxides, on whose basis complexes, with structure 295, of practically all metals have been obtained [1, vol.2 3] ... 

Arsenic, antimony, and bismuth are the metallic representatives among the fifth main-group elements. Owing to early chemotherapeutic applications a tremendous number of organo-metal derivatives has been prepared, especially of arsenic. 

Phosphorus trichloride, stannous chloride, and mercuric iodide give products of the type RHgX with mercury dimethyl, but cadmium iodide does not yield the above type, and antimony trichloride yields an organometallic eoznpound. Mercury diethyd reacts with the trichlorides of phosphorus, arsenic, and antimony to yield organo derivatives of these elements, aird with mercuric chloride it gives ethyl mercuric chloride. 

It will be seen that a number of tlie reactions afford means of obtaining organo-tballium derivatives. In the case of organo compounds of the elements of Group V., it may be stated that phosphorus and antimony chlorides yield no organo-thallium derivatives, whereas arsenic and bismuth chlorides are capable of yielding eompoimds of the type... 

There is an extensive literature on the chemistry of As, Sb, and Bi in addition to recent editions of standard textbooks, there is a book edited by Norman, which includes a chapter devoted to the coordination chemistry of these elements, as well as the article by McAuliffe in Comprehensive Coordination Chemistry (CCC, 1987). The vast organic chemistry of these elements falls outside the scope of the present chapter. Sources providing recent coverage of the organic chemistry include chapters by Wardell, in Comprehensive Organometallic Chemistry I and II, a volume in the Patai series The Chemistry of Organic Arsenic, Antimony and Bismuth Compounds), and chapters in Norman s book. These texts also list many reviews on specific classes of organo-derivatives. 

The bio-availabilities of these elements through the gastrointestinal tract vary markedly. Molybdenum, iodine, fluorine, and arsenic are apparently highly bio-available, whereas medium uptake occurs with haem iron, cobalt, zinc, chromium in the presence of a glucose tolerance factor, selenium, either as selenate or as organo selenium compounds, whereas only low bio-availability is experienced with non-haem iron,... 

Some of the difficulties in the unbiased determination of certain trace elements in biological materials may be due to problems of speciation. The range of complex organo-metallic species that can be found in nature is very wide (Frausto da Silva and Williams, 1991). In carrying out an analysis for a particular element in any type of biological fluid or tissues, major assumptions are made concerning the precise chemical composition of element species present. Different analytical techniques will have different sensitivities towards particular element species. Much of the early understanding of the special analytical problems posed by element speciation comes from studies of arsenic (Buchet et al., 1980 Buchet et al., 1981) and mercury (Clarkson, 1983). Problems with other metals remain to be resolved and may require considerable analytical sophistication such as in the analysis of chromium speciation (Urasa and Nam, 1989). 

In the environment one may be interested in some single components like NOs , Cl, NH/, Cu, etc. but nowadays there is an increasing need to know the form in which elements like copper are present, i.e. not only free metal ion concentrations but also the concentrations of the complexes and other compounds in which the metal is present and the inertness or the lability of these compounds. The reason for this need for more detailed information is the difference in toxicity of the various forms in which copper and other elements are present. For instance, the organo-mercury compounds are much more toxic than the inorganic mercury compounds whereas for arsenic the opposite is true. The detailed analysis of the forms in which elements are present is often denoted as speciation and asks, in general, for combinations of sophisticated techniques. For the moment it is difficult to see the role pTAS can play in such speciation studies but for... 

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