Electronic Structure of the Hieber Anion [Fe(CO)3(NO)]− Revisited by X‐ray Emission and Absorption Spectroscopy
Journal article, 2020

While the Hieber anion [Fe(CO)3(NO)]− has been reincarnated in the last years as an active catalyst in organic synthesis, there is still a debate about the oxidation state of the central Fe atom and the resulting charge of the NO ligand. To shed new light on this question and to understand the Fe−NO interaction in the Hieber anion, it is investigated in comparison to the formal 3d8 reference Fe(CO)5 and the formal 3d10 reference [Fe(CO)4]2− by the combination of valence-to-core X-ray emission spectroscopy (VtC-XES), X-ray absorption near-edge structure spectroscopy (XANES), and high-energy-resolution fluorescence-detected XANES. In order to extract information about the electronic structure, time-dependent density functional theory and ground-state density functional theory calculations are applied. This combination of experimental and computational methods reveals that the electron density at the Fe center of the Hieber resembles that of the isoelectronic [Fe(CO)4]2−. These  observations challenge recent descriptions of the Hieber anion and reopen the debate about the experimentally and computationally determined Fe oxidation state and charge on the NO ligand.


Group theory


X-ray absorption near edge spectroscopy



Lukas Burkhardt

Padernborn University

Yannik Vukadinovic

Padernborn University

Michal Nowakowski

Padernborn University

Aleksandr Kalinko

Padernborn University

Julian Rudolph

Padernborn University

Per-Anders Carlsson

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry

Christoph R. Jacob

Padernborn University

Matthias Bauer

Padernborn University

Inorganic Chemistry

0020-1669 (ISSN) 1520-510X (eISSN)

Vol. 59 6 3551-3561

Synergistic development of X-ray techniques and applicable thin oxides for sustainable chemistry

Swedish Research Council (VR) (2017-06709), 2018-04-04 -- 2021-12-31.

Subject Categories

Inorganic Chemistry

Physical Chemistry

Organic Chemistry

Driving Forces

Sustainable development

Areas of Advance

Materials Science



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