Synthesis, characterization and reactions of the transition metal halogenoalkyl carbocation complexes [Cp(CO)2M{η2-CH2CH(CH2)nX}]PF6 (n = 1–8, 10, M = Fe; n = 3, 4 M = Ru; X = Br, I)

The halogenoalkyl complexes [Cp(CO)2M{(CH2)nX}] (n = 3–10, 12, M = Fe; n = 5, 6, M = Ru, X = Br, I) react with Ph3CPF6 in dry CH2Cl2 to give the corresponding carbocation complexes [Cp(CO)2M{η2-(CH2CH(CH2)n−2X}]PF6 in high yields. NMR evidence indicates that the metals form metallacyclopropane type structures with the carbocation ligand. The reactions of some of the cationic complexes with NaI, PPh3, Na[Cp(CO)2Fe] and Et3N are discussed. NaI and Na[Cp(CO)2Fe] displace the halogeno-olefin, while PPh3 adds at the β-CHδ+ giving the unstable phosphonium adducts [Cp(CO)2Fe{CH2CH(PPh3)(CH2)n−2X}]PF6 which decompose to the halogeno-olefins and the cationic PPh3 complex [Cp(CO)2Fe(PPh3)]+. Et3N causes allylic deprotonation forming internal olefin complexes of the type [Cp(CO)2Fe{CH2CHCH(CH2)n−3X}]PF6.

The halogenoalkyl complexes [Cp(CO)2M{(CH2)nX}] (n = 3–10, 12, M = Fe; n = 5, 6, M = Ru, X = Br, I) react with Ph3CPF6 to give the corresponding carbocation complexes [Cp(CO)2M{η2-(CH2CH(CH2)n−2X}]PF6 in high yields. The reactions of some of the cationic complexes with NaI, PPh3 and Et3N lead to halogeno-olefin displacement, formation of the unstable phosphonium adducts [Cp(CO)2Fe{CH2CH(PPh3)(CH2)n−2X}]PF6 and allylic deprotonation, respectively.Figure optionsDownload as PowerPoint slide