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Zusammenfassung:
A novel europium (III) nitridoborate, Eu-3[B3N6], was successfully
synthesized by oxidation of Eu-3(II)[BN2](2) with Br-2 at 1073 K. The
compound crystallizes in the trigonal space group R (3) over barc
(No:167) with a=11.9370(4) angstrom, c=6.8073(4) angstrom, and Z=6. The
crystal structure of Eu-3[B3N6] consists of isolated, planar cyclic
[B3N6](9-) units which are charge-balanced by Eu3+ cations. The
oxidation state of Eu was investigated by Mossbauer spectroscopy,
electron spin resonance (ESR) spectroscopy, and quantum chemical
calculations. The Eu-151 Mossbauer spectroscopic measurement at 77 K
reveals that the main signal at delta=0.93(7) mm/s is originating from
trivalent Europium. Eu-3[B3N6] showed no ESR signal in accordance with a
non-magnetic (J=0) F-7(0) ground state of the 4f(6) configuration.
Quantum chemical calculations find six electrons in the 4f subshell
(4f(6)) of Eu indicating an oxidation state of +3. We present for the
first time the vibrational spectra of a compound with cyclic trimer
[B3N6](9-) moieties. The Raman spectrum of Eu-3[B3N6] is in good
agreement with the predicted number of modes for the spectroscopically
relevant cyclic [B3N6](9-) group with D-3h symmetry. (C) 2016 Elsevier
Inc. All rights reserved.
