Non-innocent cyanido ligands: tetracyanidoferrate(-ii) as carbonyl copycat

Jach F, Block T, Prots Y, Schmidt M, Bobnar M, Poettgen R, Ruck M, Hoehn P (2022)

Publication Type: Journal article

Publication year: 2022

Journal

Dalton Transactions Royal Society of Chemistry

DOI: 10.1039/d2dt00833e

Abstract

While a negative oxidation state occurs rarely for metals in general, this is commonly known for metal carbonyl anions, i.e. carbonyl metalates. Although CO and CN− are isoelectronic, cyanidometalates usually do not exhibit metal centers with negative oxidation states. However, we report on the electron-rich tetrahedral tetracyanidoferrate(-ii) anion [Fe(CN)4]6−, which was stabilized in (Sr3N)2[Fe(CN)4] (space group R3c, a = 702.12(2) pm, c = 4155.5(2) pm). Microcrystalline powders were synthesized by a solid-state route, single crystals were obtained from Na metal flux. In comparison to classical cyanidometalates, C-N distances are longer and stretching frequencies are lower as indicated by X-ray diffraction, IR and Raman spectroscopy. Weak C-N, strong Fe-C bonds as well as the anion geometry resemble the isoelectronic tetrahedral carbonyl ferrate [Fe(CO)4]2− 57Fe Mössbauer spectroscopic measurements reveal a negative isomer shift in agreement with substantially delocalized d electrons due to strong π back-bonding. These results point to a very similar bonding situation of both 18e tetracyanido and tetracarbonyl ferrates including non-innocent redox-active ligands and a d10 closed shell configuration on iron. Hereby, new tetracyanidoferrate(-ii) provides a missing link for a more in-depth understanding of the chemical bonding trends of highly-reduced cyanidometalates in the quest for even higher reduced transition metals in this exceptional class of compounds.

Involved external institutions

Max-Planck-Institut für Chemische Physik fester Stoffe (MPI CPfS) / Max Planck Institute for Chemical Physics of Solids DE Germany (DE) Westfälische Wilhelms-Universität (WWU) Münster DE Germany (DE)

How to cite

APA:

Jach, F., Block, T., Prots, Y., Schmidt, M., Bobnar, M., Poettgen, R.,... Hoehn, P. (2022). Non-innocent cyanido ligands: tetracyanidoferrate(-ii) as carbonyl copycat. Dalton Transactions. https://doi.org/10.1039/d2dt00833e

MLA:

Jach, Franziska, et al. "Non-innocent cyanido ligands: tetracyanidoferrate(-ii) as carbonyl copycat." Dalton Transactions (2022).

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