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Ammonothermal Synthesis of Alkali‐Alkaline Earth Metal and Alkali‐Rare Earth Metal Carbodiimides: K 5– x M x (CN 2 ) 2 +x (HCN 2 ) 1– x ( M = Sr, Eu) and Na 4.32 Sr 0.68 (CN 2 ) 2.68 (HCN 2 ) 0.32
Author(s) -
Mallmann Mathias,
Häusler Jonas,
Cordes Niklas,
Schnick Wolfgang
Publication year - 2017
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.201700238
Subject(s) - alkali metal , alkaline earth metal , chemistry , strontium , crystallography , crystal structure , powder diffraction , microcrystalline , potassium , rietveld refinement , single crystal , x ray crystallography , inorganic chemistry , diffraction , organic chemistry , physics , optics
Alkali‐alkaline earth metal and alkali‐rare earth metal carbodiimides, namely K 5– x M x (CN 2 ) 2+ x (HCN 2 ) 1– x ( x = 0 – 1) ( M = Sr, Eu) and Na 4.32 Sr 0.68 (CN 2 ) 2.68 (HCN 2 ) 0.32 , were synthesized under ammonothermal conditions in high‐pressure autoclaves. The structures of the three compounds can be derived from homeotypic K 5 H(CN 2 ) 3 and Na 5 H(CN 2 ) 3 by partial substitution of K + or Na + by Sr 2+ or Eu 2+ . The reactions were carried out in two step syntheses ( T 1 = 673 K, T 2 = 823 K) starting from sodium or potassium azide, dicyandiamide and strontium or Eu(NH 2 ) 2 , respectively. The crystal structures were solved and refined from single‐crystal X‐ray diffraction data [K 4.16 Sr 0.84 (CN 2 ) 2.84 (HCN 2 ) 0.16 : space group Im 3 m (no. 229), a = 7.8304(5) Å, Z = 2, R 1 = 0.024, wR 2 = 0.052; K 4.40 Eu 0.60 (CN 2 ) 2.60 (HCN 2 ) 0.40 : space group Im 3 m (no. 229), a = 7.8502(6) Å, Z = 2, R 1 = 0.022, wR 2 = 0.049]. In contrast to the potassium carbodiimides, the sodium‐strontium carbodiimide was only synthesized as microcrystalline powder. The crystal structure was determined by powder X‐ray diffraction and refined by the Rietveld method [Na 4.32 Sr 0.68 (CN 2 ) 2.68 (HCN 2 ) 0.32 : space group Im 3 m (no. 229), a = 7.2412(1) Å, Z = 2, R wp = 0.050]. The presence of hydrogencyanamide units ([HNCN] – ) next to carbodiimide units ([CN 2 ] 2– ) in all compounds was confirmed by FT‐IR spectroscopy.