Chloride substitution induced by mechano-chemical reactions between NaBH 4 and transition metal chlorides

Cl - to BH4- ion substitution was induced in NaBH 4 through mechano-chemical reactions with all the first period transition metal chlorides and CdCl 2. The products were identified by Rietveld refinement of powder X-ray and neutron diffraction data to be mainly Na(BH 4) 1-xCl x. These possess cubic NaCl-type structures, with unit cell parameters between 5.7801(3) and 5.6576(2), and compositions ranging from x = 0.69 (with Cu) to 0.92 (with Zn). Infrared spectroscopy of selected samples confirms the substitution through a shift of the vibrational modes of the BH4- group towards higher wavenumbers. An observed shape change of the vibrational features from Lorentzian to Gaussian is related to the presence of the transition metal. There is no correlation between x and the thermal behavior of the samples. The lowest decomposition temperature is found for the Zn containing sample (103 °C), while Cd leads to the highest value (521 °C). Their behavior is related to the presence of NaZn(BH 4) 3 and metallic Cd in the samples, respectively. © 2011 Elsevier B.V. All rights reserved.