Synthesis and Characterization of Tungsten Alkylidene and Alkylidyne Complexes Supported by a New Pyrrolide-Centered Trianionic ONO^3– Pincer-Type Ligand

Abstract

Synthetic protocols for a pyrrolide-centered ONO^3– trianionic pincer-type ligand are presented. Treating (^<i>t</i>BuO)₃WC^<i>t</i>Bu with the proligand [pyr-ONO]­H₃ (<b>2</b>) results in the formation of the trianionic pincer alkylidene complex [pyr-ONO]­WCH^<i>t</i>Bu­(O^<i>t</i>Bu) (<b>3</b>). Addition of a mild base to complex <b>3</b> provides the trianionic pincer alkylidyne complex {MePPh₃}­{[pyr-ONO]­WC^<i>t</i>Bu­(O^<i>t</i>Bu)} (<b>4</b>). All new compounds were characterized by NMR spectroscopy, combustion analysis, and, in the case of complex <b>4</b>, single-crystal X-ray crystallography. DFT calculations performed on <b>4</b> provide insight into its electronic structure and indicate that the HOMO is ligand-based and localized on the pyrrolide π orbitals