Synthesis and reactions of trifluorovinylferrocene

Trifluorovinylferrocene (1) is obtained in high yield by a Stille coupling of iodoferrocene with tributyltrifluorovinylstannane. [2+2] Cycloaddition of 1 yields the cyclobutane derivatives 2a and 2b under mild conditions. At higher temperature a defluoration reaction takes place yielding the cyclobutane derivative 3 under inert conditions whereas in the presence of air and water the cyclobuta-1,2-dion derivative 4 is formed presumably by an unusual hydrolysis of an aliphatic difluoromethylene group. Nucleophilic attack of the CF ₂ group of 1 yields specifically the trans isomer of 1,2-Diferrocenyl-1,2-difluoroethene 5. The crystal and molecular structures of 1, 2a, 2b, 3 and 5 were elucidated by X-ray diffraction.