New Polymerization Reactions Using Germylenes

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 (Mred) and an oxidant monomer (Mox). Oxidant monomers employed are p-benzo-quinones, N-phenyl-P~benzoquinone monoimines, cyclic α, β-unsaturated ketones, cyclic sulfides, and substituted acetylenes. During the copolymerization, the germylene is oxidized and an oxidant monomer is reduced (“oxidation-reduction copolymerization”). A new germanium-containing polymer having a dithiol unit in the main chain has been synthesized by the oxidative addition of poly (dithioalky-lene) toward the germylene. The reaction mechanism for the copolymerization between germylenes and p-benzoquinone derivatives has been definitely established as a biradical polymerization system involving a germyl radical and a semiquinone radical. This provides the first clear-cut evidence for a biradical mechanism in the polymerization chemistry. In addition, a ligand exchange polymerization has been found as a new concept in polymerization chemistry, which affords a polygermane of higher molecular weight.