An Investigation of Transition Metal Catalysts for Cyanohydrin Hydration: The Interface of Homogeneous and Heterogeneous Catalysis
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Acrylic monomers are important materials that represent a large portion of the economy. The current industrial synthesis hydrates cyanohydrins with sulfuric acid, a process which results in large amounts of waste and significant energy costs. A transition metal catalyzed, acid free hydration of cyanohydrins would be beneficial from both economic and environmental standpoints. However, this reaction is challenging, as many catalysts are poisoned by the cyanide released when cyanohydrins degrade. Therefore the development of a catalyst that is resistant to cyanide poisoning is the ideal method to circumvent these difficulties. This dissertation describes several cyanohydrin hydration catalysts, with an emphasis on nanoparticle catalysts. These are at the interface between the homogeneous and heterogeneous catalysts that have been explored previously for this reaction. Chapter I surveys previous studies on nanoparticle catalysts for nitrile hydration and their implications for the hydration of cyanohydrins. Chapter II reports on the homogeneous platinum catalysts [PtHCl(P(NMe2)3)2] and [PtH2(P(NMe2)3)2], exploring secondary coordination sphere effects to enhance nitrile hydration. Chapter III describes another example of this type of complex, [PtH2(P(OMe)3)2], that forms catalytically active nanoparticles under reaction conditions. Explorations of the reactivity of this catalyst with nitriles and cyanohydrins are also described in this chapter. Chapter IV investigates a silver nanoparticle catalyst with a water soluble phosphine (1,3,5-triaza-7-phosphaadamantane) ligand for its activity towards the hydration of nitriles and cyanohydrins. The results of the degradation of the nanoparticles in the presence of cyanide are also described. Chapter V reports on the preparation and examination of a solid supported nickel catalyst for cyanohydrin hydration. Finally, Chapter VI describes how these investigations have made progress towards the development of a cyanide resistant nitrile hydration catalyst. This dissertation includes previously published and unpublished co-authored material.