A study of β-hydride abstraction from alkanediyl homobimetallic complexes [{Cp(CO)2Fe}2{μ-(CnH2n)}] (n = 4–10, Cp = η5-C5H5)

The alkyl-bridged iron(II) complexes [{Cp(CO)2Fe}2{μ-(CnH2n)}] (n = 6–10, Cp = η5-C5H5) undergo both single and double hydride abstraction when reacted with one equivalent of Ph3CPF6 to give both the monocationic complexes, [{Cp(CO)2Fe}2{μ-(CnH2n−1)}]PF6, and the dicationic complexes, [{Cp(CO)2Fe}2{μ-(CnH2n−2)}](PF6)2. The ratios of monocationic to dicationic complexes decrease with the increase in the value of n. The complexes where n = 4 and 5 undergo only single hydride abstraction under similar conditions. When reacted with two equivalents of Ph3CPF6, the complexes where n = 6–10 undergo double hydride abstraction to give dicationic complexes only. In contrast, the complex where n = 5 gives equal amounts of the monocationic and the dicationic complexes, while the complex where n = 4 only gives the monocationic complex. 1H and 13C NMR data show that in the monocationic complexes one metal is σ-bonded to the carbenium ion moiety while the other is bonded in a η2-fashion forming a chiral metallacylopropane type structure. In the dicationic complexes both metals are bonded in the η2-fashion. The monocationic complexes where n = 4–6, react with methanol to give η1-alkenyl complexes[Cp(CO)2Fe(CH2)nCHCH2] (n = 2–4) as the major products and σ-bonded ether products [{Cp(CO)2Fe}2{μ-(CH2)nCH(OCH3)CH2}] as the minor products. The complex where n = 8 reacted with iso-propanol to give the η1-alkenyl complex [Cp(CO)2Fe(CH2)6CHCH2]. The dicationic complexes where n = 5, 8 and 9 were reacted with NaI to give the respective α, ω-dienes and [Cp(CO)2FeI].

The complexes [Cp(CO)2Fe2μ-(CH2)n] (n = 5–10, Cp = η5-C5H5) undergo both single and double hydride abstraction to give the monocationic complexes, [Cp(CO)2Fe2μ-(CnH2n−1)]PF6, and the dicationic complexes, [Cp(CO)2Fe2μ-(CnH2n−2)](PF6)2 upon reaction with Ph3CPF6. The complex where n = 4 gives only the monocationic complex [{Cp(CO)2Fe}2μ-(C4H7)]PF6.Figure optionsDownload as PowerPoint slide