Highly Active Manganese Hydrogenation Catalysts

To develop greener, sustainable, and more cost-effective chemical processes it is highly important to replace precious metal catalysts with Earth-abundant non-precious metal catalysts. Among these, Mn comprises a promising candidate as it is the third most abundant transition metal in the Earths crust. It is inexpensive, and exhibits a rather low environmental impact and, thus, Mn is a metal with low safety concerns. Currently, 250 ppm residual levels of Mn considered acceptable in pharmaceuticals. These facts represent a distinct advantage when compared with the = 10 ppm prescribed for most other transition metals. The main objective of this project is the discovery of novel catalytic reactions based on our recent discoveries in the field of Mn(I) chemistry. We will explore here the full catalytic potential of Mn(I) systems for the synthesis fine chemicals. We hope to discover new reactions and intend to apply the new catalysts for reactions which thus far have been difficult to achieve with base metals. In particular, we will synthesize a series of rationally-designed Mn-based catalysts and evaluate their catalytic performance for (i) alkene and alkyne hydrogenations, (ii) hydrogenation of polar double and triple bonds, and (iii) hydroformylation using alkenes in combination with molecular hydrogen and carbon monoxide (syn-gas) to obtain alcohols. These studies will make use of the full toolbox of techniques available for modern synthetic chemistry: experimental-based catalyst design, catalytic studies and mechanistic studies. This project is expected to generate fundamental understanding of new concepts in bond activation and may lead to efficient new manganese catalysis as well as reactions formerly restricted to noble metals, even surpassing these, and will result in the development of new, environmentally benign catalytic processes.

To develop greener, sustainable, and more cost-effective chemical processes it is highly important to replace precious metal catalysts with Earth-abundant non-precious metal catalysts. Among these, Mn comprises a promising candidate as it is the third most abundant transition metal in the Earth's crust. It is inexpensive, and exhibits a rather low environmental impact and, thus, Mn is a metal with low safety concerns. The main objective of this project was to establish novel catalytic reactions based on our recent discoveries in the field of Mn(I) chemistry. We explored the full catalytic potential of Mn(I) systems for the synthesis fine chemicals. We synthesized a series of rationally-designed Mn-based catalysts and evaluated their catalytic performance for (i) alkene, alkyne, ketones, and nitrile hydrogenations, (ii) dehydrogenative silylation of alkenes and hydroborations of alkenes and alkynes, and (iii) carbon monoxide functionalization. These studies made use of the full toolbox of techniques available for modern synthetic chemistry: experimental-based catalyst design, catalytic studies and mechanistic studies. This project generated fundamental understanding of new concepts in bond activation and lead to the discovery of efficient new manganese catalysis as well as reactions formerly restricted to noble metals, even surpassing these, and will result in the development of new, environmentally benign catalytic processes.