Cationic Bis-N-Heterocyclic Carbene (NHC) Ruthenium Complex: Structure and Application as Latent Catalyst in Olefin Metathesis

An unexpected cationic bis-N-heterocyclic carbene (NHC) benzylidene ether based ruthenium complex (2a) was prepared through the double incorporation of an unsymmetrical unsaturated N-heterocyclic carbene (U-2-NHC) ligand that bore an N-substituted cyclododecyl side chain. The isolation and full characterization (including X-ray diffraction studies) of key synthetic intermediates along with theoretical calculations allowed us to understand the mechanism of the overall cationization process. Finally, the newly developed complex 2a displayed interesting latent behavior during ring-closing metathesis, which could be switched on under acidic conditions.