Catalytic and Electrocatalytic Transformations with Palladium and Nickel : Scope and mechanistic investigations

Abstract: The work presented in this thesis is based on methodology development and mechanistic investigations using heterogeneous palladium and nickel catalysts. Following the introduction (Chapter 1), Chapter 2 presents a summary of the synthesis and characterization of the MOF-supported Pd catalysts (Pd @ MOF) that are used in this thesis. Chapters 3, 4 and 5 are based on the use of heterogeneous Pd @ MOF catalysts for CC bond forming reactions, whilst Chapter 6 deals with the use of nickel foam for hydrogenation reactions. In Chapter 3, the speciation of the ligandless Suzuki-Miyaura reaction catalyzed by Pd @ MOF is investigated. Here, questions regarding the composition, structure and reactivity of leached palladium are studied by means of electrospray ionization mass spectrometry (ESI-MS), density-functional theory (DFT) calculations, nuclear magnetic resonance (NMR) spectroscopy and scanning-transmission electron microscopy (STEM). (Paper I)The next chapter (Chapter 4) deals with the study of the Mizoroki-Heck reaction catalyzed by Pd @ MOF under working conditions. In this study, catalyst activation, catalyst deactivation and the role of the MOF support are studied. (Paper II) Chapter 5 concerns the use of MOF-supported Pd (II) complexes for the aerobic homocoupling of boronic acids. A mild oxidation method for regenerating active catalytic palladium species, which enables its recyclability, is described. (Paper III)The last chapter (Chapter 6) describes the use of a commercially available nickel foam for the stereoselective semireduction of alkynes using electrochemically generated hydrides from acidic water. As the method tolerates numerous functional groups, it could be applied to a large variety of alkynes. The use of deuterated solvents provided easy access to a library of deuterated Z -olefins. (Paper IV)