Alkaline earth mediated carbon monoxide activation

• Main Author: Anker, Mathew
• Other Authors: Hill, Michael
• Published: University of Bath 2017
• Subjects: 546
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.720654

The aim of this thesis is to investigate the synthetic utility of insertion reactions with Group two complexes, specifically towards the activation of the small molecular gas; carbon monoxide. Extension of this Group two mediated reactivity into catalytic regimes exploits both σ–bond metathesis and insertion chemistries with hydride sources such as PhSiH3 or HBpin to generate value added chemicals. Chapter Two demonstrates organoisocyanates are readily converted to methyl amines through hydrodeoxygenation with HBpin in the presence of the β–diketiminato magnesium catalyst, Ib. A series of catalytically relevant species have been identified and fully characterized through stoichiometric reactivity studies. These data suggest that overall reduction and C–O activation occur through the intermediacy of well–defined magnesium formamidato and magnesium boryloxide species. This reaction is further explored through a DFT study which complements the experimental findings. Chapter Three explores the reaction between both β–diketiminato magnesium, Ih, and calcium, Ii, hydride complexes with carbon monoxide, resulting in the isolation of dimeric cis–enediolate species by the reductive coupling of two CO molecules. Under catalytic conditions with PhSiH3, an observable magnesium formyl species may be intercepted for the mild reductive cleavage of the CO triple bond to a methane analogue in the case of Ih. The related calcium formyl species could not be identified but under identical catalytic conditions reduced CO to a methoxysilane species, demonstrating the variability in the chemistries of the group two elements. Chapter Four investigates the carbonylation of a range of in situ generated β–diketiminato Ae–NRRʹ (Ae = Mg or Ca, R = H or Me and Rʹ = H, Alkyl or aryl) complexes, resulting in the isolation of a number of formamidate complexes and including a carbenic formamide dimagnesium species. The hydrodeoxygenation chemistry that was explored in Chapter Two is then extended to the range of isolated compounds providing a novel route to methyl amines.