Exploring Simple Catalyst for Transfer Hydrogenation of Ketones and Photocatalytic Hydrogen Production Using Homogeneous Metal Complexes

Abstract

Transfer hydrogenation has been recognized to be an important synthetic method in both academic and industrial research to obtain valuable products including alcohols. Transition metal catalysts based on precious metals, such as Ru, Rh and Ir, are typically employed for this process. This thesis starts with a study on the potential of an Fe based complex carrying a PNP ligand (2,6-{Ph2PNH}2(NC5H3)) to function as an active transfer hydrogenation catalyst for the conversion of ketones to alcohols. During the analysis of the performance parameters of this potential catalyst, it was discovered that the added base, KOtBu, was the actual catalyst. Other bases were explored as catalysts for this transformation as well as the general performance features of this simple alkali metal base. In a separate project described in Chapter 3, the search for catalysts shifted focus to a study of the potential of a series of first row transition metal-based complexes supported by a bis(thioether)pyridine “SNS” ligand for photocatalytic hydrogen production. This initial study led to the observation that the Fe complex [Fe(k3-2,6-(CH3SCH2)2C5H3N)Br2]2 was a capable photocatalyst for H2 production in combination with a photosensitizer (Ru(bpy)3)2+) and an electron donor (triethanolamine). Although water was initially believed to be the source of protons that were reduced to H2, analysis of control experiments pointed to the hydrogen source being the electron donor.