Functional Group Tolerant Olefin Metathesis Catalysts Based on N-Heterocyclic Carbene Complexes of High Oxidation State Molybdenum Imido Alkylidenes

• Applicant: Professor Dr. Michael R. Buchmeiser
• Subject Area: Preparatory and Physical Chemistry of Polymers ; Inorganic Molecular Chemistry - Synthesis and Characterisation
• Term: from 2015 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 271749009

N-Heterocyclic carbene (NHC) adducts of high oxidation state Mo-imido alkylidenes shall be prepared. For these purposes, different NHCs, i.e. small, large, strongly basic or nucleophilic ones, shall be used. Variations in catalyst structure shall further comprise of different anionic ligands such as alkoxides, phenoxides, carboxylates, iso(thio)cyanates as well as of different imido-ligands. The chosen approach will allow elucidating the activating effect of the NHC on the metal alkylidene in terms of ligand dissociation and concomitant formation of cationic alkylidene species. Furthermore, the role of the anionic ligands will be elucidated. Notable, metal complexes with mixed anionic ligands are accessible. In terms of different types of metathesis reactions for which the novel systems shall be used, we wish to address olefin metathesis reactions relevant to both organic synthesis and polymer chemistry. These will comprise of ring-closing metathesis (RCM), cross-metathesis (CM), ring-opening cross metathesis (ROCM) enyne / ene-diyne metathesis and self-metathesis (SM) reactions as well as of ring-opening metathesis polymerization (ROMP), acyclic diene metathesis (ADMET) polymerization and the cyclopolymerization of diynes. With ionic catalysts, all the envisaged reaction types including polymerization reactions can be carried out under biphasic conditions. With the exception of cyclopolymerization, continuous supported ionic liquid phase (SILP) conditions can be applied. In CM, enyne and SM reactions, but also in ROMP and cyclopolymerization, special attention will be devoted to stereoselectivity. The proposed work will not only broaden the understanding about high oxidation state metal alkylidene NHC complexes, but also offer a new class of functional group tolerant, highly active stereo- and regioselective catalysts for olefin metathesis-based C-C coupling reactions.

• DFG Programme: Research Grants