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Abstract. Na 3 [BN 2 ] and Na 2 K[BN 2 ] were obtained as white polycrystalline powders from the reaction of the respective binary mixtures NaNH 2 :NaBH 4 and NaNH 2 :KBH 4 in molar ratio 2:1 at 873 K and 683 K, respectively, in an argon stream. According to the results of thermal analysis measurements, both compounds are thermally stable only up to 954 K (Na 3 [BN 2 ]) and 712 K (Na 2 K[BN 2 ]), respectively, decomposing under evolution of alkali metal and nitrogen to yield hexagonal BN as final residue, which was identified from powder patterns.

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Na3[BN2] and Na2K[BN2]: A Known and a Novel Alkali Metal DinitridoborateObtained via Mild Thermal Dehydrogenation. -Na 3 [BN 2 ] (I) and Na 2 K[BN 2 ] (II) are obtained from the reaction of the respective binary mixtures NaNH2:NaBH4 and NaNH2:KBH4 in a molar ratio of 2:1 via thermal dehydrogenation (873 K and 683 K, resp., under Ar). They are thermally stable up to 954 K (I) and 712 K (II) and decompose under evolution of alkali metal and nitrogen to yield hexagonal BN as final residue. The compounds crystallize in the β-Li 3 [BN 2 ] type (I) (space group P2 1 /c, Z = 4) and in the Na2KCuO2 type (tetragonal space group I4/mmm, Z = 2, powder XRD). The crystal structure of (II) is composed of linear [N-B-N] 3anions centering elongated M14 rhombic dodecahedra which are formed by 8 Na and 6 K. The [BN2]@Na8K6 polyhedra are condensed via common tetragonal faces to generate a 3D arrangement. Vibrational spectra of the title compounds are discussed. -(KOZ, C.; ACAR, S.; PROTS, Y.; HOEHN*, P.; SOMER, M.; Z. Anorg. Allg. Chem. 640 (2014) 2, 279-285, http://dx.doi.org/10.1002/zaac.201300445 ; MPI Chem. Phys. fester Stoffe,