Activation, Reactivity and Dynamics of Manganese Pincer Complexes in Hydrogenation Catalysis

Abstract

The growing demands for sustainable chemical technologies have prompted a wave of searching new catalysts based on earth-abundant metals. In the field of (de)hydrogenation catalysis, however, the huge performance gap is commonly seen between the 3d-metal-based catalysts and their noble metal counterparts, which largely hampers their practical applications. In particular, while the Mn-catalyzed (de)hydrogenation has witnessed significant progress since the pioneering work by Beller and co-workers in 2016, most of the reported systems still require relatively high catalyst loadings. Apart from developing new synthetic methodologies based on the hydrogen transfer reactivity of Mn, searching highly active catalysts for (de)hydrogenation reactions therefore remains one of the central topics in Mn chemistry. The current approach to catalyst development is mainly based on the screening of the ligand backbones that proved to be effective for noble metal-based catalysts. However, the screening assessments with the reaction yields as the sole performance metrics do not probe the intrinsic reactivities of the catalysts and can easily result in the overlook of the potential ones due to suboptimal condition choice. In this thesis, we demonstrate in this thesis that the catalyst performance is defined by a complex reaction network comprised of multiple stages of catalyst operation, that is catalyst activation, deactivation, and catalytic turnover. The reactivity of the catalyst itself and the reaction environment of each process determine synergistically the catalytic performance. As a result, the catalytic transformation should be viewed from the system perspective with the performance being a dynamic and highly condition-dependent characteristic.