From d8 to d1: Iron(0) and Iron(I) Complexes Complete the Series of Eight Fe Oxidation States within the TIMMNMes Ligand Framework

Gravogl L, Keilwerth M, Körber E, Heinemann FW, Meyer K (2024)

Publication Type: Journal article

Publication year: 2024

Journal

DOI: 10.1021/acs.inorgchem.4c02129

Abstract

Reduction of the ferrous precursor [(TIMMN^Mes)Fe(Cl)]⁺ (1) (TIMMN^Mes = tris-[(3-mesitylimidazol-2-ylidene)methyl]amine) to the low-valent iron(0) complex [(TIMMN^Mes)Fe(CO)3] (2) is presented, where the tris(N-heterocyclic carbene) (NHC) ligand framework remains intact, yet the coordination mode changed from 3-fold to 2-fold coordination of the carbene arms. Further, the corresponding iron(I) complexes [(TIMMN^Mes)Fe(L)]⁺ (L = free site, η¹-N2, CO, py) (3) are synthesized and fully characterized. Complexes 1-3 demonstrate the notable steric and electronic flexibility of the TIMMN^Mes ligand framework by variation of the Fe-N anchor and Fe-carbene distances and the variable size of the axial cavity occupation. This is further underpinned by the oxidation of 3-N2 in a reaction with benzophenone to yield the corresponding, charge-separated iron(II) radical complex [(TIMMN^Mes)Fe(OCPh2)]⁺ (4). We found rather surprising similarities in the reactivity behavior when going to low- or high-valent oxidation states of the central iron ion. This is demonstrated by the closely related reactivity of 3-N2, where H atom abstraction with TEMPO triggers the formation of the metallacycle [(TIMMN^Mes*)Fe(py)]⁺ (5), and the reactivity of the highly unstable Fe(VII) nitride complex [(TIMMN^Mes)Fe(N)(F)]³⁺ to give the metallacyclic Fe(V) imido complex [(TIMMN^MesN)Fe(N^Mes)(MeCN)]³⁺ (6) upon warming. Thus, the employed tris(carbene) chelate is not only capable of stabilizing the superoxidized Fe(VI) and Fe(VII) nitrides but equally supports the iron center in its low oxidation states 0 and +1. Isolation and characterization of these zero- and monovalent iron complexes demonstrate the extraordinary capability of the tris(carbene) chelate TIMMN to support iron in eight different oxidation states within the very same ligand platform.

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APA:

Gravogl, L., Keilwerth, M., Körber, E., Heinemann, F.W., & Meyer, K. (2024). From d8 to d1: Iron(0) and Iron(I) Complexes Complete the Series of Eight Fe Oxidation States within the TIMMNMes Ligand Framework. Inorganic Chemistry. https://doi.org/10.1021/acs.inorgchem.4c02129

MLA:

Gravogl, Lisa, et al. "From d8 to d1: Iron(0) and Iron(I) Complexes Complete the Series of Eight Fe Oxidation States within the TIMMNMes Ligand Framework." Inorganic Chemistry (2024).

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