Ammonia-Borane Dehydrogenation Promoted by an Osmium Dihydride Complex: Kinetics and Mechanism

作者：Esteruelas Miguel A^*; Lopez Ana M; Mora Malka; Onate Enrique

来源：ACS Catalysis, 2015, 5(1): 187-191.

DOI：10.1021/cs501536d

• ammonia-borane dehydrogenation
• osmium
• dihydride
• dihydrogen
• kinetic
• DFT
• mechanism

Complex OsH2(CO)((PPr3)-Pr-i)(2), generated from OsH2(CO)(eta(2)-CH2=CHEt)((PPr3)-Pr-i)(2) by dissociation of the olefin, promotes the release of 1 equiv of H-2 from ammonia-borane and the formation of polyaminoborane. The dehydrogenation rate law is of the form d[H-2]/dt = k[Os] with activation parameters of Delta H double dagger = 19.6 +/- 2.5 kcal-mol(-1) and Delta S double dagger = 6 +/- 9 cal.mol(-1).K-1. On the basis of kinetic results, spectroscopic NMR observations, and DFT. calculations, the dihydride-dihydrogen derivative OsH2(eta(2)-H-2) (CO)((PPr3)-Pr-i)(2) is proposed as a key intermediate for the dehydrogenation. Its formation involves the concerted BR- and NH-hydrogen transfers from the amine-borane to the metal center and to a hydride ligand, respectively.

• 出版日期2015-1