Research on two independent projects is presented:(1) Homogeneous cascade catalysis has been used for the hydrogenation of CO2 to methanol as it allows for rational tuning of catalyst reactivity and lower reaction temperatures compared to heterogeneous catalysis. Still, temperatures and pressures far above ambient conditions are required for hydrogenation. Performing cascade CO¬2 reduction electrochemically could result in milder reaction conditions. To this end, a series of bis(diphosphine) metal hydrides was synthesized. Their reactivity towards the reduction of methyl formate and formaldehyde, the final two intermediates in a proposed reaction pathway between CO2 and methanol, was investigated in alcohol solvents and acetonitrile (or acetonitrile substitutes). In alcohol solvents, transesterification of methyl formate and protonation of the metal hydride [HPt(dmpe)2]+ outcompetes any possible hydride transfer to methyl formate. Because the hydride donor ability, or hydricity, of the metal hydrides tested is known in acetonitrile, studying reactivity in acetonitrile allowed for the bracketing of previously unreported methyl formate and formaldehyde hydride affinity values. The hydride affinity of methyl formate and formaldehyde were bracketed between 26.4 – 34.0 kcal/mol and 49.9 – 57.6 kcal/mol, respectively. This result represents an important step in the rational construction of an electrochemical cascade pathway for CO2 reduction to methanol.
(2) Concerted proton-electron transfer (CPET) pathways can sometimes lead to lower energetic pathways for small molecule oxidation reactions. There is evidence to suggest that incorporating hydrogen bond donors/acceptors in the outer sphere of catalysts can promote CPET. To investigate this idea, syntheses of complexes containing the ligand N,N′-bis((6-(dimethylamino)pyridin-2-yl)methyl)-N,N′-dimethylethane-1,2-diamine (LDMA) were explored. This ligand features pendant dimethyl amine groups that appear to promote CPET water oxidation in previous work with cobalt. Substituting cobalt with group 8 metals (Fe, Ru, Os) may impart enhanced water oxidation reactivity and/or stability of oxidized products (key for verifying a CPET mechanism for water oxidation). Thus, the attempted syntheses of group 8 complexes of LDMA are discussed with only the iron LDMA complex, with purported structure [FeLDMA(CH3CN)2][OTf]2 or FeLDMA(OTf)2, yielding clean product and spectroscopic characterization by 1H NMR.