As the developed world seeks to reduce the dependence upon fossil fuels, amine boranes have received increased interest as a clean, stable hydrogen source. This thesis sought to scrutinise the mechanism of amine borane dehydrocoupling proposed by Hill and provide quantitative evidence for the dependence of dehydrocoupling activity upon identity of the metal centre. This work led to a refined mechanism, incorporating proton-assisted β-hydride elimination steps, occurring via potentially concerted processes. A pathway to account for the previously unreported reactivity of [R2N-BH2]2 to ultimately afford [HB(NR2)2] is also included. A dependence upon the identity of the metal centre on the dehydrocoupling activity was found, identifying a decrease in reactivity with increasing ionic radius and decreasing cation charge density as each group is descended. This thesis showed that the mechanism of secondary amine borane dehydrocoupling by d0 reagents is complex, suggesting that a generic mechanism which fully describes dehydrocoupling of all amine boranes would be too much of an oversimplification.
|Date of Award||20 Jun 2014|
|Supervisor||Michael Hill (Supervisor)|