Improved Trianionic Pincer Ligand Synthesis for Cyclic Polymer Catalysts

Abstract

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≡CtBu)(THF)] (7) are reported. The synthesis of the [tBuOCO]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 Cipso 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.