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Type‐II Clathrate Na 24‐ δ Ge 136 from a Redox‐Preparation Route
Author(s) -
Feng XianJuan,
Bobnar Matej,
Lerch Swantje,
Biller Harry,
Schmidt Marcus,
Baitinger Michael,
Strassner Thomas,
Grin Yuri,
Böhme Bodo
Publication year - 2021
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202102082
Subject(s) - chemistry , redox , amorphous solid , inorganic chemistry , powder diffraction , crystallography , analytical chemistry (journal) , organic chemistry
Abstract The metastable type‐II clathrate Na 24‐ δ Ge 136 was obtained from Na 12 Ge 17 by applying a two‐step procedure. At first, Na 12 Ge 17 was reacted at 70 °C with a solution of benzophenone in the ionic liquid (IL) 1,3‐dibutyl‐2‐methylimidazolium‐bis(trifluoromethylsulfonyl) azanide. The IL was inert towards Na 12 Ge 17 , but capable of dissolving the sodium salts formed in the redox reaction. By annealing at 340 °C under an argon atmosphere, the X‐ray amorphous intermediate product was transformed to crystalline Na 24‐ δ Ge 136 ( δ ≈2) and α‐Ge in an about 1 : 1 mass ratio. The product was characterized by X‐ray powder diffraction, chemical analysis, and 23 Na solid‐state NMR spectroscopy. Metallic properties of Na 24‐ δ Ge 136 were revealed by a significant Knight shift of the 23 Na NMR signals and by a Pauli‐paramagnetic contribution to the magnetic susceptibility. At room temperature, Na 24‐ δ Ge 136 slowly ages, with a tendency to volume decrease and sodium loss.