Carborate anions as Tools for “pseudo-naked” Magnesium and Calcium Cations – CarMaCat

Metal-based Lewis acid catalysis is widespread as a powerful and versatile method for the catalysis of various organic transformations. Traditionally and almost exclusively, metal Lewis acids consists of a central metal cation surrounded/coordinated by a number of supporting ligands for stability and solubility, yet resulting into a significantly decreased electrophilicity of the metal center. “Naked”/Ligand-free metal cations stand as the ultimate targets to maximize electrophilic activation that may lead to effective/unprecedented substrates functionalization whether in a stoichiometric or catalytic manner. But access to stable ligand-free metal ions (or “pseudo-naked” ions) in solution has to date remained a major challenge.
The present project will primarily aim at the synthesis and reactivity studies of unprecedented “pseudo-naked” Mg2+ and Ca2+ di-cations only stabilized by weak interactions with carborate and ammonia-borate anions of the type [R-CB11Cl11]- and [R3NB12Cl11]-, which are the most chemically inert weakly coordinating anions known to date. Besides the latter targets, [(NHC)Mg]2+ di-cations and two-coordinate MgII species of the type [(NHC)Mg–X]+ will also be aimed at through NHC coordination in order to tune MgII Lewis acidity and incorporate a reactive [Mg–X]+ moiety of interest for substrates functionalization. The reactivity (and the potential as catalysts) of all these unprecedented cations with small molecules of interest (CO2, H2, unsaturated substrates) will be studied through their use in hydro-functionalization and hydrogenation catalytic reactions. Their potential utility for the transformation of biomass-related molecules (such as alkyl aryl ethers) to added value molecules will also be evaluated.