Novel polymerizations of germylenes and their reaction mechanisms

Novel copolymerizations for the synthesis of germanium‐containing polymers using a divalent germanium species, germylene, have been developed. The copolymerization involves a redox process between a germylene (M_red) and an oxidant monomer (M_ox) such as p‐benzoquinones, cyclic α,β‐unsaturated ketones, and substituted acetylenes. A new germanium‐containing polymer having a germanium‐sulfur bond unit in the main chain has been synthesized by the oxidative addition of a poly(dithioalkylene) toward the germylene. A ligand exchange polymerization has been developed as a new polymerization reaction affording a polygermane. The reaction mechanism of the copolymerization between germylene and p‐benzoquinone derivatives has definitely been established as a biradical polymerization system involving a germyl radical and a semiquinone radical, providing the first clear‐cut evidence for a biradical mechanism in the polymerization chemistry.