title: Ammine magnesium borohydride complex as a new material for hydrogen storage: structure and properties of Mg(BH4)2.2NH3.
abstract: The ammonia complex of magnesium borohydride Mg(BH4)2.2NH3 (I), which contains 16.0 wt % hydrogen, is a potentially promising material for hydrogen storage. This complex was synthesized by thermal decomposition of a hexaaammine complex Mg(BH4)2.6NH3 (II), which crystallizes in the cubic space group Fm3 m with unit cell parameter a=10.82(1) A and is isostructural to Mg(NH3) 6Cl2. We solved the structure of I that crystallizes in the orthorhombic space group Pcab with unit cell parameters a=17.4872(4) A, b=9.4132(2) A, c=8.7304(2) A, and Z=8. This structure is built from individual pseudotetrahedral molecules Mg(BH4)2.2NH3 containing one bidentate BH4 group and one tridentate BH4 group that pack into a layered crystal structure mediated by N-H...H-B dihydrogen bonds. Complex I decomposes endothermically starting at 150 degrees C, with a maximum hydrogen release rate at 205 degrees C, which makes it competitive with ammonia borane BH 3NH3 as a hydrogen storage material.
authors.affiliation: General Electric Global Research Center, Niskayuna, New York 12309, USA. soloveichik@crd.ge.com
authors.forename: Grigorii
authors.initials: G
authors.lastname: Soloveichik
authors.forename: Jae-Hyuk
authors.initials: JH
authors.lastname: Her
authors.forename: Peter W
authors.initials: PW
authors.lastname: Stephens
authors.forename: Yan
authors.initials: Y
authors.lastname: Gao
authors.forename: Job
authors.initials: J
authors.lastname: Rijssenbeek
authors.forename: Matt
authors.initials: M
authors.lastname: Andrus
authors.forename: J-C
authors.initials: JC
authors.lastname: Zhao