Redox shuttling and catalysis – exploiting novel anionic aluminyl-ligand and aluminyl-d-block metal synergy

• Applicant: Debotra Sarkar, Ph.D.
• Subject Area: Inorganic Molecular Chemistry - Synthesis and Characterisation
• Term: from 2022 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 502364945

Catalysis is perhaps the most important application of the chemical sciences developed over the past century. Enhancement of the rate and selectivity of a chemical transformation through the intervention of a compound that is regenerated at the end of the reaction represents a potent tool for assembling complex molecules in a resource-efficient manner. However, this field is particularly dominated by the precious transition metal owing to their redox flexibility. Thus, molding compounds derived from the abundant, chemically benign lighter p-block elements (e.g., Al, Si, etc.) through molecular design to interact with industrially relevant molecules in a 'Transition Metal like' fashion represents an exciting fundamental chemical challenge offering very high potential rewards. Aluminium is one of the most abundant elements in the earth's crust by mass (following oxygen and silicon). Recently, low valent aluminium compounds, possessing a nucleophilic Al centre with an anionic charge, namely aluminyl anion ([R2Al:]-M+), which are in the +I oxidation state, with comparatively small HOMO‐LUMO gaps, showed promising activity in potentially mimicking the ambiphilic reactivity of transition metals. Nevertheless, utilization of aluminyl anion in redox-based catalysis remains challenging due to the difficulties associated with reductive elimination, and therefore release of the functionalized substrates. The vision of this project is centered around two inter-related and increasingly ambitious scientific aims:i) Al(I)/Al(III) catalysis: The initial goal of this project is to develop novel anionic aluminium(I) species with usable [n/(n+2)] redox flexibility through the systematic design of supporting scaffold and use this insight to establish main group redox catalysis of hydroelementation chemistry (e.g., hydrogenation, hydroboration, hydrosilylation, etc.).ii) Bimetallic catalysis: Albeit, our prime goal of this project is to procure TM-free catalysis based on aluminyl system. However, the strong transformative effect of the ambiphilic aluminyl ligand to the TM (derived from the strong σ-donation and Lewis acidity of Al) and aluminyl-transition metal cooperativity could also be useful for activation of more challenging inert bonds (e.g., sp3 C-H bond of alkane). Thus, we hypothesize that combining aluminyl ligand and transition metal in a covalently linked bimetallic system will enable the facial novel bond activation processes with redox flexibility to enhance cooperative stoichiometric and catalytic processes (e.g., catalytic dehydrogenation of alkane).

• DFG Programme: WBP Fellowship
• International Connection: United Kingdom
• Host: Professor Simon Aldridge, Ph.D.