title: Mechanistic investigation on the formation and dehydrogenation of calcium amidoborane ammoniate.
abstract: Possessing high H(2)  capacities and interesting dehydrogenation behavior, metal amidoborane ammoniates were prepared by reacting Ca(NH(2) )(2) , MgNH, and LiNH(2)  with ammonia borane to form Ca(NH(2) BH(3) )(2) ⋅2 NH(3) , Mg(NH(2) BH(3) )(2) ⋅NH(3) , and Li(NH(2) BH(3) )(2) ⋅NH(3)  (LiAB⋅NH(3) ). Insight into the mechanisms of amidoborane ammoniate formation and dehydrogenation was obtained by using isotopic labeling techniques. Selective (15) N and (2) H labeling showed that the formation of the ammoniate occurs via the transfer of one H(N) from ammonia borane to the [NH(2) ](-)  unit in Ca(NH(2) )(2)  giving rise to NH(3)  and [NH(2) BH(3) ](-) . Supported by theoretical calculations, it is suggested that the improved dehydrogenation properties of metal amidoborane ammoniates compared to metal amidoboranes are a result of the participation of a strong dihydrogen bond between the NH(3)  molecule and [NH(2) BH(3) ](-) . Our study elucidates the reaction pathway involved in the synthesis and dehydrogenation of Ca(NH(2) BH(3) )(2) ⋅2 NH(3) , and clarifies our understanding of the role of NH(3) , that is, it is not only involved in stabilizing the structure, but also in improving the dehydrogenation properties of metal amidoboranes.
authors.affiliation: Dalian Institute of Chemical Physics, 457 Zhongshan Road, Dalian 116023, PR China.
authors.forename: Yong Shen
authors.initials: YS
authors.lastname: Chua
authors.forename: Wen
authors.initials: W
authors.lastname: Li
authors.forename: Wendy J
authors.initials: WJ
authors.lastname: Shaw
authors.forename: Guotao
authors.initials: G
authors.lastname: Wu
authors.forename: Tom
authors.initials: T
authors.lastname: Autrey
authors.forename: Zhitao
authors.initials: Z
authors.lastname: Xiong
authors.forename: Ming Wah
authors.initials: MW
authors.lastname: Wong
authors.forename: Ping
authors.initials: P
authors.lastname: Chen
mesh_terms: D000641:Ammonia / Q000737:chemistry; D001880:Boranes / Q000737:chemistry*; D017610:Calcium Compounds / Q000737:chemistry*; D006865:Hydrogenation
chemical_list: D001880:Boranes; D017610:Calcium Compounds; D000641:Ammonia