Molecularly Controlled Catalysis – Targeting Synergies Between Local and Non‐local Environments

Abstract

Future chemicals should preserve the efficiency of their function while reducing hazards and waste. In this context, catalysis – a fundamental pillar of Green Chemistry – is still the most effective technique capable of meeting societal requirements while offering sustainability. To further push the boundaries of catalysis and respond to these challenges, a clear understanding of the molecular level interactions is essential. To succeed, we believe it is necessary to consider the transition metal catalyst as a molecular system encompassing a local and non‐local environment. The synergistic effects that are taking place between the ligand, the metal center, and their surrounding environments primarily determine the efficiency of the bond making and breaking processes. This Concept provides tools for identifying, implementing, and combining these effects to control catalysis directly at a molecular level.

Alcohol-Assisted Hydrogenation of Carbon Monoxide to Methanol Using Molecular Manganese Catalysts

“…The first process is the activation of CO by base-catalyzed carbonylation of the alcohol to the corresponding formate ester. , The base also activates the precursor complex [Mn­(MACHO- i Pr)­(CO) 2 Br] by the elimination of HBr to the active hydrogenation catalyst I . A putative catalytic cycle for the hydrogenation of the formate ester to methanol is illustrated in Scheme via the widely inferred metal–ligand cooperation (MLC) mechanism. ,,− Plausible alternatives are, however, also conceivable, involving, for example, activation of the CO unit by Na + instead of H + at the ligand amide group or heterolytic H 2 cleavage at a cationic Mn 1+ complex after carboxylate, alcoholate, or CO dissociation (see the Supporting Information for a schematic representation). ,− …”

Acceptorless Dehydrogenation of Methanol to Carbon Monoxide and Hydrogen using Molecular Catalysts

“…[17g, 21a,b] Complex 1 generates the reactive species Ru II complex (I) comprising the cooperative M-N site. [22] Similarly, the manganese complex 6 can enter an analogous manifold upon activation with the base. It is previously well-established that in the presence of alcohol, complex I forms the Rualcoholate complex II.…”

Systematic Variation of 3d Metal Centers in a Redox-Innocent Ligand Environment: Structures, Electrochemical Properties, and Carbon Dioxide Activation

“…binding affinity, define the prevailing mechanistic route, which is directly linked to the catalytic performance. However, only a limited number of studies report on the systematic variation of the metal center within an identical ligand framework in relation to CO 2 electroreduction (Figure A). − The majority of these studies rely on the so-called “noninnocent” ligands because these ligands are often perceived as beneficial for the activity by sharing excess electron density (redox noninnocence) or relaying protons (chemical noninnocence). − The resulting complex interplay of ligand- and metal-centered processes renders deconvolution of the individual contributions rather challenging . By contrast, systematic variations of the metal centers with redox-innocent ligands, such as pincer platforms, − remain insufficiently investigated in the frame of CO 2 electroreduction (Figure B).…”