Carbazole pincer-type ligands offer a unique opportunity to tailor the nucleophilicity of metal-carbon multiple bonds via the inorganic enamine effect. Isolobal with organic enamines, an inorganic enamine orbital interaction occurs when an amido nitrogen-atom lone pair is collinear with a metal-carbon multiple bond. For example, the previously reported trianionic pincer-type ligand [CF3-ONO]H3 enhances the nucleophilicity of tungsten-alkylidene and tungsten-alkylidyne complexes. However, [CF3-ONO]H3 contains flexible flanking biaryl rings adjacent to the central amine that create an inherent twist across the pincer backbone. Preventing the twist, a new rigid trianionic [ONO]3- C2v-symmetric carbazole-based pincer ligand is synthesized to constrain the amido lone-pair to be perfectly collinear with metal-carbon multiple bonds. Tungsten alkylidene and anionic tungsten alkylidyne complexes were synthesized bearing the new carbazole pincer ligand. DFT calculations reveal that the nitrogen atom lone pair is nearly collinear to the alkylidyne π-orbitals in anionic alkylidyne complex bearing the rigid ligand suggesting an inorganic enamine orbital overlap within the alkylidyne. In addition to the new pincer ligand, a chelating ligand capable of cycloaddition with metal-carbon multiple bonds is explored.

New ligands for tuning metal-carbon multiple bonds.

ACS Spring Meeting 2021

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