We use cookies to ensure that we give you the best experience on our website. By continuing to browse this repository, you give consent for essential cookies to be used. You can read more about our Privacy and Cookie Policy.

Durham e-Theses
You are in:

Exploration of new routes to boranes and carboranes

Gaffney, Piers Robert James (1988) Exploration of new routes to boranes and carboranes. Masters thesis, Durham University.



The crystal chemistry of binary metal borides in the composition range M(_4) to MB(_12) and the hydrolytic chemistry of reactive metal borides to give boranes are reviewed. The thermal interconversion reactions of the smaller volatile boranes from B(_2)H(_6) to B(_10)H(_14) is critically examined and a rationalisation of their reactions with the transient Lewis acid species {BH(_3)), (B(_3)H(_7)) and (B(_4)H(_8)) is developed. This approach reveals a pattern of step-wise cage-growth for nido boranes which first seem to ligate a BH(_3) unit and then eliminate H(_2) giving the next higher homologue. Also, a structure-reactivity relationship for B(_2)H(_6) and the arachno boranes is suggested where the terminal hydrogens of the BH(_2) groups are thought to possess hydridic character which dominates their reactions with the Lewis acid intermediates. This work is partially extended to the cage-expansion and pyrolysis reactions of the anionic boron hydrides. A detailed review is presented of the pyrolysis of tetraalkylammonium borohydrides to give [B(_10)H(_10)](^2-) and [B(_12)H(_12)](^2-) in high yield. A study of the acidic hydrolysis of MgB(_2) under a wide range of conditions is reported. The reactions of MgB(_2) with 100% H(_3)PO(_4) and with 7M H(_3)PO(_4) under the influence of ultrasonics are found to be promising methods for increasing the borane yield. The anions [B(_12)H(_120](^2-), [B(_10)H(_10)](_2) and possibly [B(_9)H(_14)](^-) are shown to be important products from MgB(_2) hydrolysis. A mechanism is proposed for this reaction incorporating initial production of CB(_6)H(_9)](^-) which is protonated to give B(_6)H(_10); degradation of this borane in the acidic solution is thought to account for generation of B(_5)H(_9) and B(_4)H(_10) which are the only other major volatile boron hydride products. Finally, some attempted "one-pot” carborane syntheses using MgB(_2) as the boron source are discussed. [brace not closed]

Item Type:Thesis (Masters)
Award:Master of Science
Thesis Date:1988
Copyright:Copyright of this thesis is held by the author
Deposited On:08 Feb 2013 13:37

Social bookmarking: del.icio.usConnoteaBibSonomyCiteULikeFacebookTwitter