Linking Metallacycle Transfer with Ring‐Opening Metathesis to Generate Polyacetylenes of Unprecedented Structure

A hafnium-based bicyclic precursor (COT-2B-Hf) has been prepared that enables tandem Hf/E metallacycle transfer (E = main group element) and the ring-opening metathesis polymerization (ROMP) of cyclooctatetraene (COT) units to generate a new family of structurally unique polyacetylenes. Highlights from this work include a tellurophene-grafted polyacetylene, poly-COT-2B-Te, and a polyacetylene with unsaturated vinyl side chains, poly-COT-2B-vinyl. The resulting polymers can be processed into films that yield optical band gaps as low as 1.6 eV, representing promising new architectures for the optoelectronics community.