Dynamic Covalent Polymers Based upon Carbene Dimerization

Significance

The synthesis of a new class of dynamic, covalent polymers is reported, in which the well-documented dimerization of carbenes is employed as a reversible, carbon-carbon bond-forming reaction. Under basic conditions, bis(benz­imidazole) starting materials were converted into enetetraamine-based oligomers or polymers. The efficiency of the polymerization process was highest for monomers bearing sterically unhindered N-substituents, as judged by the ratio of polymer to free carbene. The dynamic nature of the polymerization was probed by a variety of experiments, including demonstrations of depolymerization by heating, dilution, or by addition of end-capping groups such as 3. Reaction of palladium(II) chloride with polymer 2b resulted in the formation of a metal carbenoid polymer identical in composition to that prepared in an earlier study by Bielawski and coworkers (J. Am. Chem. Soc. 2005, 127, 12496-12497).