C–H activation by a terminal imidoiron(III) complex to form a cyclopentadienyliron(II) product

Imido complexes of the late transition metals have the ability to activate C–H bonds through the abstraction of hydrogen atoms from hydrocarbons. This paper describes the apparent hydrogen atom transfer from cyclopentadiene (CpH) to the isolable imidoiron(III) complex LMeFeNAd (LMe = 2,4-bis(2,6-diisopropylphenylimido)pent-3-yl; Ad = 1-adamantyl) in the presence of 4-tert-butylpyridine (tBupy). The isolated product is not the amidoiron(II) complex, but instead it is LMeFe(Cp)(tBupy), the result of amido protonation by additional CpH. The crystal structures of both LMeFeCp and LMeFe(Cp)(tBupy) are presented, and in the latter compound the Fe–C bonds are longer than in any previously characterized cyclopentadienyliron complex.

Graphical abstractCyclopentadiene reacts with the imidoiron(III) complex LMeFeNAd (LMe = 2,4-bis(2,6-diisopropylphenylimido)pent-3-yl; Ad = 1-adamantyl) in the presence of 4-tert-butylpyridine (tBupy). The isolated product is not the amidoiron(II) complex, but instead the result of amido protonation by additional CpH. The iron–Cp distance in LMeFe(Cp)(tBupy) is the longest ever characterized.Figure optionsDownload full-size imageDownload as PowerPoint slideResearch highlights► Hydrogen atom abstraction by an iron–imido complex. ► Synthesis and characterization of diketiminate–Cp–iron complexes. ► Unprecedentedly long Cp–iron distance modulated by pyridine coordination.