Boron hydrides detection

Sowinski and Suffet 297) have used GC/MS to detect boron hydrides at trace levels, whereas Blum and Richter (298) have used capillary columns in the combined GC/MS of a series of phenylboronate derivatives. There have also been recent applications of GC/MS to the TMS derivatives of inorganic anions (299). The TMS derivatives of ammonium arsenates. 

Sowinski, E. J., Suffet, I. U. Gas-chromatographic detection and confirmation of volatile boron hydrides at trace levels. Anal Chem. 46, 1218 (1974)... 

The inability of such photolyzate solutions to hydroborate 1-octyne rules out the presence of neutral boron hydrides. However, the detection of HD, upon the work-up with DOAc, and the formation of undeuterated toluene, upon treatment of the photolyzate with benzyl chloride and deuterolytic work-up, clearly support the presence of borohydrides, such as 45 (6). Finally, evidence supporting the generation of sodium diphenylborate(I) (46) or a similar product was obtained by conducting the photolysis in the presence of diphenylacetylene. Since monomeric 46 is formally isoelectronic with a carbene, adducts like 48... 

Sawinski and Suffet applied a Melpar flame photometric system to the determination of boron hydrides, the detector was fitted with an optical filter having a maximum transmittance of 546nm. The column packing was OV-1 on Chromosorb W. Down to 0,7ng decaborane could be detected with this equipment,... 

Phillips and Timms [599] described a less general method. They converted germanium and silicon in alloys into hydrides and further into chlorides by contact with gold trichloride. They performed GC on a column packed with 13% of silicone 702 on Celite with the use of a gas-density balance for detection. Juvet and Fischer [600] developed a special reactor coupled directly to the chromatographic column, in which they fluorinated metals in alloys, carbides, oxides, sulphides and salts. In these samples, they determined quantitatively uranium, sulphur, selenium, technetium, tungsten, molybdenum, rhenium, silicon, boron, osmium, vanadium, iridium and platinum as fluorides. They performed the analysis on a PTFE column packed with 15% of Kel-F oil No. 10 on Chromosorb T. Prior to analysis the column was conditioned with fluorine and chlorine trifluoride in order to remove moisture and reactive organic compounds. The thermal conductivity detector was equipped with nickel-coated filaments resistant to corrosion with metal fluorides. Fig. 5.34 illustrates the analysis of tungsten, rhenium and osmium fluorides by this method. 

A modified stepwise hydroboration avoiding the use of lithium aluminum hydride has also been developed (Schane 23.30). It was discovered that trialkylsilane reacts rapidly with boron trihalide to form unsolvated dihaloborane. Subsequent reaction with alkenes in the presence of sufficient boron trihalide occurs rapidly at -78°C to afford alkylboron dihalides without detectable contamination by dialkylboron halides. If additional equivalents of both trialkylsilane and alkene are added, dialkylboron halides are obtained. The methodology has been successfully applied to the synthesis of l,l,I-tris(dichloroboryl)alkanes, important precursors for dicarbapentaboranes. ... 

---