Catalytic amine-borane dehydrogenation by a PCP-pincer palladium complex: a combined experimental and DFT analysis of the reaction mechanism

• Published in: Dalton transactions : an international journal of inorganic chemistry 2013-03, Vol.42 (10), p.3533-3541
• Main Authors: Rossin, Andrea, Bottari, Giovanni, Lozano-Vila, Ana M, Paneque, Margarita, Peruzzini, Maurizio, Rossi, Andrea, Zanobini, Fabrizio
• Format: Article
• Language: English
• Subjects: Byproducts; Catalysis; Catalysts; Computation; Dehydrogenation; Equivalence; NMR spectroscopy; Reaction mechanisms
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c2dt32273k

Catalytic dehydrogenation of ammonia-borane (NH(3)·BH(3), AB) and dimethylamine borane (NHMe(2)·BH(3), DMAB) by the Pd(II) complex [((tBu)PCP)Pd(H(2)O)]PF(6) [(tBu)PCP = 2,6-C(6)H(3)(CH(2)P(t)Bu(2))(2)] leads to oligomerization and formation of spent fuels of general formula cyclo-[BH(2)-NR(2)](n) (n = 2,3; R = H, Me) as reaction byproducts, while one equivalent of H(2) is released per amine-borane equivalent. The processes were followed through multinuclear ((31)P, (1)H, (11)B) variable temperature NMR spectroscopy; kinetic measurements on the hydrogen production rate and the relative rate constants were also carried out. One non-hydridic intermediate could be detected at low temperature, whose chemical nature was explored through a DFT modeling of the reaction mechanism, at the M06//6-31+G(d,p) computational level. The computational output was of help to propose a reliable mechanistic picture of the process.