title: Ammine Calcium and Strontium Borohydrides: Syntheses, Structures, and Properties.
abstract: A new series of solvent- and halide-free ammine strontium metal borohydrides Sr(NH3 )n (BH4 )2 (n=1, 2, and 4) and further investigations of Ca(NH3 )n (BH4 )2 (n=1, 2, 4, and 6) are presented. Crystal structures have been determined by powder XRD and optimized by DFT calculations to evaluate the strength of the dihydrogen bonds. Sr(NH3 )(BH4 )2 (Pbcn) and Sr(NH3 )2 (BH4 )2 (Pnc2) are layered structures, whereas M(NH3 )4 (BH4 )2 (M=Ca and Sr; P21 /c) are molecular structures connected by dihydrogen bonds. Both series of compounds release NH3 gas upon thermal treatment if the partial pressure of ammonia is low. Therefore, the strength of the dihydrogen bonds, the structure of the compounds, and the NH3 /BH4 (-) ratio for M(NH3 )n (BH4 )m have little influence on the composition of the released gasses. The composition of the released gas depends mainly on the thermal stability of the ammine metal borohydride and the corresponding metal borohydride.
authors.affiliation: Center for Materials Crystallography, Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, Aarhus University, Langelandsgade 140, 8000, Aarhus C, Denmark.
authors.forename: Lars H
authors.initials: LH
authors.lastname: Jepsen
authors.affiliation: High Temperature Energy Materials Research Center, Korea Institute of Science and Technology, Seoul, 136-791, Republic of Korea.
authors.forename: Young-Su
authors.initials: YS
authors.lastname: Lee
authors.affiliation: Laboratory of Crystallography, DQMP, University of Geneva, 1211, Geneva, Switzerland.
authors.forename: Radovan
authors.initials: R
authors.lastname: Černý
authors.affiliation: Center for Materials Crystallography, Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, Aarhus University, Langelandsgade 140, 8000, Aarhus C, Denmark.
authors.forename: Ram S
authors.initials: RS
authors.lastname: Sarusie
authors.affiliation: High Temperature Energy Materials Research Center, Korea Institute of Science and Technology, Seoul, 136-791, Republic of Korea.
authors.forename: Young Whan
authors.initials: YW
authors.lastname: Cho
authors.affiliation: Interdisciplinary Nanoscience Center (iNANO) and Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000, Aarhus C, Denmark.
authors.forename: Flemming
authors.initials: F
authors.lastname: Besenbacher
authors.affiliation: Center for Materials Crystallography, Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, Aarhus University, Langelandsgade 140, 8000, Aarhus C, Denmark. trj@chem.au.dk.
authors.forename: Torben R
authors.initials: TR
authors.lastname: Jensen
mesh_terms: D000641:Ammonia / Q000737:chemistry*; D001894:Borohydrides / Q000138:chemical synthesis / Q000737:chemistry*; D002118:Calcium / Q000737:chemistry*; D015394:Molecular Structure; D033362:Powder Diffraction; D017550:Spectroscopy, Fourier Transform Infrared; D013324:Strontium / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D001894:Borohydrides; D000641:Ammonia; D002118:Calcium; D013324:Strontium
keywords: alkaline earth metals; boron; hydrogen; reaction mechanisms; structure elucidation