Carbenes are strong donor ligands widely used in metal catalyzed organic reactions. Bidentate carbenes are potentially more stable due to the chelating effect. A possible pathway for tuning the metal reactivity is bite angle variation.  Donor abilities of imidazole-derived bis N-heterocyctic carbenes (NHCs), bis acyclic diaminocarbenes, bitriazole bis(NHCs), and �abnormal� C4-bound bis(NHCs), and thus their trans influence and effect on metal electrophilicity, were studied using methylisocyanide as an IR probe. Donor abilities of ligands were correlated with structural parameters such as carbene dihedral angle. Acetonitrile adducts of [(chelate)Pd]2+  complexes were examined as catalysts for electrophilic cyclization of  acetylenic aldehydes with alcohols to form cyclic alkenyl ethers, hydroarylation of alkynes with aromatic compounds and polarized Nazarov cyclizations of dialkenyl ketones. The most effective catalysts were those with ligands which were identified as less effective donor ligands by MeNC IR probe studies.

Effects of ligand structure and donor ability on electrophilic catalytic reactions of palladium bis-carbene complexes

241st National Meeting (2011)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.