Improved Trianionic Pincer Ligand Synthesis for Cyclic Polymer Catalysts

An easier, safer, and scalable approach to the synthesis of a trianionic pincer ligand and its use in the preparation of the Mo cyclic polymer catalyst [O2C­((p-OMe-C6H4)­C)­Mo­(η2-CHC t Bu)­(THF)] (7) are reported. The synthesis of the [ t BuOCO]­Me2 (1) ligand is simplified to a reaction that allows scaling up, thus reducing the main barrier to accessing cyclic polymer catalysts. The synthesis allows for the derivatization of the C ipso carbon of the central ring of the pincer. Taking advantage of this, a deuterium atom was substituted for kinetic isotope measurements. Complex 7 was tested for activity in the polymerization of phenylacetylene. Confirmation of the cyclic polymer topology comes from gel permeation chromatography (GPC), dynamic light scattering (DLS), and intrinsic viscosity (η) measurements.