A Simple and Efficient Approach to Synthesize Amidoborane Ammoniates: Case Study for Mg(NH2BH3)2(NH3)3 with Unusual Coordination Structure

Published

July 14, 2012

Author(s)

Xiangdong Kang, Hui Wu, Junhong Luo, Wei Zhou, Ping Wang

Abstract

Metal amidoborane ammoniates are a new type of promising hydrogen storage materials consisting of metal cation, [NH₂BH₃] anionic unit and NH₃ ligand. Herein, we report a new reactive ball milling approach for preparation of magnesium amidoborane ammoniate, Mg(NH₂BH₃)₂(NH₃)₃. Our study found that mechanically milling the NH₃BH₃/MgH₂ mixture in a 2:1 molar ration under NH₃ atmosphere can readily produce Mg(NH₂BH₃)₂(NH₃)₃. Its crystal structure was successfully determined by a combination of X-ray diffraction (XRD) analysis and first-principles calculations. This compound possesses a novel ordered structure with alternating layers of Mg(NH₃)₆⁶⁺ hexamminemagnesium cations and Mg(NH₂BH₃)₄^2- complex anions, in which Mg²⁺ exhibits both VI and IV coordinations. Property measurements found that Mg(NH₂BH₃)₂(NH₃)₃ can release 7 equivalent (10.6 mass%) of H6d2^ upon heating up to 300 ° C in a closed system. A combination of XRD, Fourier transformation infrared spectroscopy (FTIR), and solid-state ¹¹B MAS NMR techniques has been employed to characterize Mg(NH₂BH₃)₂(NH₃)₃ and its dehydrogenation product. A series of control experiments have also been conducted to gain insight into the formation mechanism of Mg(NH₂BH₃)₂(NH₃)₃.

Citation

Journal of Materials Chemistry

Volume

22

Pub Type

Journals

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Keywords

hydrogen storage

Citation

Kang, X. , Wu, H. , Luo, J. , Zhou, W. and Wang, P. (2012), A Simple and Efficient Approach to Synthesize Amidoborane Ammoniates: Case Study for Mg(NH₂BH₃)₂(NH₃)₃ with Unusual Coordination Structure, Journal of Materials Chemistry, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=911033 (Accessed September 17, 2024)