D. Mennie, P. Craig
1994
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Journal
Main Group Metal Chemistry
Abstract
Use of sodium triethylboron hydride for derivatization of mercury compounds for analysis produces ethyl mercury species. Introduction In order to identify and analyse organometallic species (eg butyltins, methyl mercury) from the natural environment it is necessary to release the organometallic moiety from the normally strong binding to proteinaceous material in natural waters or sediments. This may be done by use of Grignard reagents or boron species, normally sodium borohydride or sodium tetraethylboron (illustrated in Schemes 1 and 2). NaB (C2H5) 4 CH3Hg + > CH3HgC2H5 [1] NaBH< (C«H,)3Sn* > (C4H„)3SnH [2] Release in a volatile form is necessary to allow chromatographic separation of similar components of the same metal that may be present (eg the mixed butyl tins from marinas, harbours etc). The process of release (derivatization) is assumed not to perturb the amount or character of the organometallic compound present (eg dismutation is assumed not to take place). Numerous experiments have been carried out to demonstrate that this central assumption is correct. Nevertheless, as the case of the naturally occurring methyl arsenic species demonstrates, much potentially interesting information may be lost using the normal methods of derivatization, as only the organometallic moiety and not the counter ion is identified. Sodium triethylboron hydride (NaB(C2H5)3H) is used extensively in organic synthesis where it is an excellent source of nucleophilic hydride. Indeed it is colloquially known as "Superhydride"* Potentially then it could be considered as a derivatizing reagent for organometallic species in a similar (or more effective) manner than eg sodium borohydride. This latter reagent is known to be less effective at derivatizing organometallics from more heavily and generally polluted environments and the more nucleophilic triethylboron hydride reagent could be considered as a potentially better reagent in these circumstances.