Peierls‐Distorted Monoclinic MnB 4 with a MnMn Bond

Tetraborides of chromium and manganese exhibit an unusual boron‐atom framework that resembles the hypothetical tetragonal diamond. They are believed to be very hard. Single crystals of MnB 4 have now been grown. The compound crystallizes in the monoclinic crystal system (space group P 2 1 / c ) with...

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Bibliographic Details
Published in:Angewandte Chemie International Edition 2014-02, Vol.53 (6), p.1684-1688
Main Authors: Knappschneider, Arno, Litterscheid, Christian, George, Nathan C., Brgoch, Jakoah, Wagner, Norbert, Beck, Johannes, Kurzman, Joshua A., Seshadri, Ram, Albert, Barbara
Format: Article
Language:English
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Summary:Tetraborides of chromium and manganese exhibit an unusual boron‐atom framework that resembles the hypothetical tetragonal diamond. They are believed to be very hard. Single crystals of MnB 4 have now been grown. The compound crystallizes in the monoclinic crystal system (space group P 2 1 / c ) with a structure that has four crystallographically independent boron‐atom positions, as confirmed by 11 B MAS‐NMR spectroscopy. An unexpected short distance between the Mn atoms suggests a double Mn–Mn bond and is caused by Peierls distortion. The structure was solved using group‐subgroup‐relationships. DFT calculations indicate Mn I centers and paramagnetism, as confirmed by magnetic measurements. The density of states shows a pseudo‐band gap at the Fermi energy and semiconducting behavior was observed for MnB 4 .
ISSN:1433-7851
1521-3773
DOI:10.1002/anie.201306548