Ruthenium-Based Hydrogenation and Frustrated Lewis Pair Chemistry

Since the discovery of catalytic hydrogenation, the field of transition metal-based hydrogenation catalysis has grown significantly. Recently, main group systems have demonstrated the capability to perform some of the same catalytic processes. Frustrated Lewis pairs (FLP), the combination of sterically encumbered Lewis acids and Lewis bases, are able to activate a variety of small molecules. The research presented in this thesis investigates main group and transition metal-based catalytic hydrogenation, as well as stoichiometric transformations with main group systems. A variety of ruthenium N-heterocyclic carbene (NHC) complexes were generated with polyethylene glycol (PEG) on the NHC to impart water-solubility. These hydrogenation catalysts were used to hydrogenate nitrile butadiene rubber (NBR) to hydrogenated nitrile butadiene rubber (HNBR). The PEG lengths had minimal effect on the conversion of NBR in solution phase. For the hydrogenation of NBR latex, a correlation was observed between the PEG length and the activity. A family of phosphinimines with different steric and electronic properties was synthesized from the Staudinger reaction between alkynyl-phosphines and azido-phosphine-boranes. Cyclization of these products can be induced thermally or by the addition of catalytic amounts of B(C6F5)3. Upon cyclization, a net trans-hydroboration was observed on the exocyclic alkene. A novel geminal boron-sulfur FLP was synthesized from the hydroboration of sulfur-alkynes. These systems demonstrated FLP-type chemistry such as the activation of terminal alkynes. Interestingly, the frustration was a result of the steric conflict between the tert-butyl substituent on the carbon and the p-tolyl substituent on the Lewis basic sulfur. This FLP-type reactivity can altered upon isomerization of the complex, forming the classical Lewis pair adduct. Finally, metal-free transformation of 3-ethylidene-6-vinyltetrahydro-2H-pyran-2-one was investigated. The Lewis acid B(C6F5)3 was shown to catalytically hydrogenate the allyl functionality of the substrate, as well as catalytic hydrosilylation of the conjugated alkene.Ph.D