期刊
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
卷 140, 期 13, 页码 4569-4579出版社
AMER CHEMICAL SOC
DOI: 10.1021/jacs.7b13526
关键词
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资金
- ACS PRF [54436-ND4, 55595-DNI4]
- R.K. Mellon Foundation
- National Science Foundation [CBET-1653392]
- Ohio Supercomputer Center [PCS0201-5]
Thermodynamic hydricities (AGH-) in acetonitrile and dimethyl sulfoxide have been calculated and experimentally measured for several metal-free hydride donors: NADH analogs (BNAH, CN-BNAH, Me-MNAH, HER), methylene tetrahydromethanopterin analogs (BIMH, CAFH), acridine derivatives (Ph-AcrH, Me2N-AcrH, T-AcrH, 4OH, 2OH, 3NH), and a triarylmethane derivative (6OH). The calculated hydricity values, obtained using density functional theory, showed a reasonably good match (within 3 kcal/mol) with the experimental values, obtained using potential pK(a) and hydride-transfer methods. The hydride donor abilities of model compounds were in the 48.7-85.8 kcal/mol (acetonitrile) and 46.9-84.1 kcal/mol (DMSO) range, making them comparable to previously studied first-row transition metal hydride complexes. To evaluate the relevance of entropic contribution to the overall hydricity, Gibbs free energy differences (AGH-) obtained in this work were compared with the enthalpy (Delta H-H(-)) values obtained by others. The results indicate that, even though Delta H-H(-) values exhibit the same trends as Delta G(H)(-), the differences between room-temperature Delta G(H)(-) and Delta H-H(-) values range from 3 to 9 kcal/mol. This study also reports a new metal-free hydride donor, namely, an acridine-based compound 3NH, whose hydricity exceeds that of NaBH4. Collectively, this work gives a perspective of use metal-free hydride catalysts in fuel-forming and other reduction processes.
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