Ferrocenyl substituted chlorostilbenes and butadienes

The readily accessible α-chlorophosphonates (OCH2CMe2CH2O)P(O)CH(Cl)C6H4-4-R [1: R=Me (a), OMe (b), Cl (c), H (d)] react with ferrocenecarboxaldehyde in the presence of NaH [Horner–Wadsworth–Emmons reaction] to give good yields of ferrocenyl substituted chlorostilbenes. The novel bis ferrocenyl butadiene C5H5FeC5H4CHCHC(CN)CHC5H4FeC5H5 (9) as well as the ferrocenyl 2-cyano-1,3-butadienes 4-RC6H4CHCHC(CN)CHC5H4FeC5H5 [R=Me (10a), OMe (10b), Cl (10c)] have been obtained by using the new allylphosphonate (OCH2CMe2CH2O)P(O)CH2C(CN)CHC5H4FeC5H5 (8); the latter compound was prepared in good yields by the reaction of the Baylis–Hillman adduct, C5H5FeC5H4CH(OH)C(CN)CH2 (7), with the chlorophosphite (OCH2CMe2CH2O)PCl. The electrochemical behavior of the ferrocenyl compounds thus synthesized has been studied; two reversible one-electron processes are observed in the case of compound 9 suggesting a cooperative interaction between the two ferrocenyl residues.