Metal‐Free Ring‐Opening Metathesis Polymerization with Hydrazonium Initiators

The ring‐opening metathesis polymerization (ROMP) of cyclopropenes using hydrazonium initiators is described. The initiators, which are formed by the condensation of 2,3‐diazabicyclo[2.2.2]octane and an aldehyde, polymerize cyclopropene monomers by a sequence of [3+2] cycloaddition and cycloreversion reactions. This process generates short chain polyolefins (Mn≤9.4 kg mol−1) with relatively low dispersities (Đ≤1.4). The optimized conditions showed efficiency comparable to that achieved with Grubbs’ 2nd generation catalyst for the polymerization of 3‐methyl‐3‐phenylcyclopropene. A positive correlation between monomer to initiator ratio and degree of polymerization was revealed through NMR spectroscopy. The metal‐free ring‐opening metathesis polymerization (ROMP) of 3,3‐disubstituted cyclopropenes with hydrazonium initiators ultilizing the principle of carbonyl‐olefin metathesis is demonstrated.