(η5-C5H5)-Ring alkylation reaction with the C5H5 anion: towards the construction of tri-Fe complex Fe{[μ,η5:η4-5-exo-(1′-C5H4)C5H5]Fe(CO)2(PPh3)}2

The reaction of (η5-C5H5)Fe(CO)2I with C5H5M (M=Na, Li) in the presence of PPh3 gives the Cp-ring alkylation η4-Fe products 10a,b. The compounds 10a,b could be deprotonated with n-BuLi to generate 12. When 12 reacts with FeCl3, the reaction produces the tri-Fe complex 6, Fe{[μ,η5:η4-5-exo-(1′-C5H4)C5H5]Fe(CO)2(PPh3)}2, whose hydride abstraction with Ph3CPF6 results in 13, [Fe{[μ,η5:η5-1-(1′-C5H4)C5H4]Fe(CO)2(PPh3)}2][PF6]2. A similar strategy was applied in the preparation of penta-Fe complex 15, Fe[μ-η5-C5H3-1,3-{(C5H5-5′-exo-η4)Fe(CO)2(PPh3)}2]2, which has four η4-Fe arms attached to a ferrocene core. The compound 12, upon treatment with the W(CO)3(EtCN)3 then MeI sequence, gives the dimetallic η4-Fe, η5-W complex 17. The endo-hydride of 17 could be abstracted with Ph3CPF6 to result in 18 whose reaction with C5H5Na proceeds smoothly with the Cp-ring alkylation and gives η4-Fe products 19a,b. Treatment of 19a,b with n-BuLi, followed by the W(CO)3(EtCN)3 then MeI sequence yields the trimetallic η5-W, η4-Fe, η5-W complex 20.