title: The effect of the NH2 substituent on NH3: hydrazine as an alternative for ammonia in hydrogen release in the presence of boranes and alanes.
abstract: Potential energy surfaces for H(2) release from hydrazine interacting with borane, alane, diborane, dialane and borane-alane were constructed from MP2/aVTZ geometries and zero point energies with single point energies at the CCSD(T)/aug-cc-pVTZ level. With one borane or alane molecule, the energy barrier for H(2)-loss of approximately 38 or 30 kcal mol(-1) does not compete with the B-N or Al-N bond cleavage ( approximately 30 or approximately 28 kcal mol(-1)). The second borane or alane molecule can play the role of a bifunctional catalyst. The barrier energy for H(2)-elimination is reduced from 38 to 23 kcal mol(-1), or 30 to 20 kcal mol(-1) in the presence of diborane or dialane, respectively. The mixed borane-alane dimer reduces the barrier energy for H(2) release from hydrazine to approximately 17 kcal mol(-1). A systematic comparison with the reaction pathways from ammonia borane shows that hydrazine could be an alternative for ammonia in producing borane amine derivatives. The results show a significant effect of the NH(2) substituent on the relevant thermodynamics. The B-N dative bond energy of 31 kcal mol(-1) in NH(2)NH(2)BH(3) is approximately 5 kcal mol(-1) larger than that of the parent BH(3)NH(3). The higher thermodynamic stability could allow hydrazine-borane to be used as a material for certain energetic H(2) storage applications.
authors.affiliation: Department of Chemistry, University of Leuven, B-3001 Leuven, Belgium. minh.nguyen@chem.kuleuven.be
authors.forename: Nguyen
authors.initials: N
authors.lastname: Vinh-Son
authors.forename: Saartje
authors.initials: S
authors.lastname: Swinnen
authors.forename: Myrna H
authors.initials: MH
authors.lastname: Matus
authors.forename: Minh Tho
authors.initials: MT
authors.lastname: Nguyen
authors.forename: David A
authors.initials: DA
authors.lastname: Dixon
mesh_terms: D000409:Alanine / Q000737:chemistry*; D000641:Ammonia / Q000737:chemistry*; D001880:Boranes / Q000737:chemistry*; D002384:Catalysis; D002621:Chemistry / Q000379:methods; D006834:Hydrazines / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry*; D008968:Molecular Conformation; D012984:Software; D013816:Thermodynamics
chemical_list: D001880:Boranes; D006834:Hydrazines; C029424:hydrazine; D000641:Ammonia; D006859:Hydrogen; D000409:Alanine