Crystal structure of phenanthrenide salts stabilized by 15-crown-5 and 18-crown-6

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Eichstaedt, Natalie ; van der Zwan, Kasper P. ; Mayr, Lina ; Siegel, Renée ; Senker, Jürgen ; Breu, Josef:
Crystal structure of phenanthrenide salts stabilized by 15-crown-5 and 18-crown-6.
In: Zeitschrift für Naturforschung B. Bd. 77 (2022) Heft 4-5 . - S. 197-201.
ISSN 1865-7117
DOI: https://doi.org/10.1515/znb-2021-0177

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Abstract

Potassium 15-crown-5 phenanthrenide and potassium 18-crown-6 phenanthrenide were synthesized and characterized by powder X-ray diffraction and K-39 solid state NMR spectroscopy. While the radical carbanion is very reactive in solution, the crystals are stable and storable under inert atmosphere. For 15-crown-5, a sandwich-like complex of potassium is formed with two molecules of crown ether per potassium resulting in a coordination number of 10. For the larger 18-crown-6 ligand, a 1:1 complex is obtained and a coordination number of 6 for the potassium cation. In neither crystal structure solvent molecules are incorporated. The 15-crown-5 compound crystallizes faster and is less soluble in THF as compared to the 18-crown-6 compound. Both compounds form solid phenanthrenide that is easy to handle and can be applied for reduction reactions.