Synthesis of cationic cobaltocenophane monomers: Isomerization and ring-opening metathesis polymerization

We report the synthesis of cyclic cobaltocenium olefins (cationic cobaltocenophane or ansa-cobaltocenium). This cyclic cobaltocenium is prepared by ring-closing metathesis (RCM) of diallyl cobaltocenium, which isomerizes into two different cobaltocenium dienes. The isomerization of the terminal alkene at higher temperature results in thermodynamically more stable internal alkene, which is supported by the computational calculation. RCM of these isomers produces two different cyclic cobaltocenium monomers [3]- and [4]-ansa-cobaltocenium, which are further evaluated as monomers for ring-opening metathesis polymerization (ROMP). The results indicate that both ansa-cobaltocenium monomers can be copolymerized with cyclooctene derivatives towards main-chain cobaltocenium-containing copolymers. [Display omitted] •Cationic cobaltocenophane or ansa-cobaltocenium was prepared by ring-closing metathesis of diallyl-cobaltocenium isomers.•Thermodynamics and the ring strain energy dictate the formation of cyclic cobaltocenium.•ansa-Cobaltocenium was copolymerized via ring-opening metathesis polymerization.