Sodium borohydride hydrazinates: synthesis, crystal structures, and thermal decomposition behavior

Metallic borohydride hydrazinates are novel boron-and nitrogen-based materials that appear to be promising candidates for chemical hydrogen storage. Herein, sodium borohydride hydrazinates, including NaBH4 center dot N2H4 and NaBH4 center dot 2N(2)H(4), were synthesized via a facile solution synthesis approach based on the solid-liquid reaction between NaBH4 and hydrazine in tetrahydrofuran (THF) solution. The crystal structure of NaBH4 center dot 2N2H4 was solved to a monoclinic structure with unit cell parameters a = 8.4592(2) angstrom, b = 11.7131(2) angstrom, c = 6.4584(1) angstrom, and beta = 100.0777(14)degrees, with space group A1a1 (9). Each Na+ ion interacts with four neighboring N2H4 molecules, leading to the formation of Na-4[N2H4](4)(4+) cationic chains along the a direction. Such cationic chains are surrounded by BH4- anions. The NaBH4 center dot xN(2)H(4) (x = 1, 2) was characterized by Powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), and mass spectroscopy (MS) to obtain a full picture of the relationship of the structure to the decomposition, which will be useful for future work on borohydride hydrazinates or the study of other B-N materials. Furthermore, magnesium borohydride hydrazinates were synthesized by ball milling the sodium borohydride hydrazinates with magnesium borohydride, and their thermal decomposition was investigated as well.