Initial developments within group 2 chemistry led to the chemistry being described as ‘lanthanide mimetic’ however, over the last 10 years group 2 catalysis has emerged in its own right, making these comparisons unjustified. Development of this catalytic chemistry has, until now, largely focussed upon the use of protic reagents in order to achieve turnover. Reported in this thesis is the development of magnesium hydride chemistry for both stoichiometric and catalytic purposes. Reported in chapter 2 of this thesis, is the use of the pharmaceutically relevant magnesium dihydropyridide complexes and explores their use as hydride transfer reagents with respect to a representative ketone, benzophenone, whilst further study with various different isocyanate reagents with differing electronic and steric demands provides divergent reactivity. Extension of this chemistry with respect to carbodiimides provides a series of N-heterocyclic guanidinates in all but one case. The chemistry described in chapters 3-6 investigates the use of magnesium hydrides in catalysis. Using the commercially available hydridic pinacol borane (HBpin) reagent a series of catalytic reactions with respect to pyridines (chapter 3), nitriles (chapter 4), iso-nitriles (chapter 5) and heterocumulenes (chapter 6) are investigated. In each case, studies have sought to underpin the catalytic reactivity by examining the single steps of the proposed catalytic cycle via a series of stoichiometric reactions which has allowed for the isolation and characterisation of numerous potential catalytic intermediates. Monitoring of these catalytic reactions in situ with NMR spectroscopy, combined with kinetic analysis, has allowed for further information to be obtained with regards to the mechanism and calculation of the activation energy parameters associated with each reaction.
|Date of Award||8 Jun 2015|
|Supervisor||Michael Hill (Supervisor)|