期刊
CHEMICAL SCIENCE
卷 11, 期 6, 页码 1683-1690出版社
ROYAL SOC CHEMISTRY
DOI: 10.1039/c9sc05565g
关键词
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资金
- U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences as part of the Center for Light Energy Activated Redox Processes (LEAP) Energy Frontier Research Center [DE-SC0001059]
- National Science Foundation [DGE1122492]
The high-valent nickel(iii) complex Ni(pyalk)(2)(+) (2) was prepared by oxidation of a nickel(ii) complex, Ni(pyalk)(2) (1) (pyalk = 2-pyridyl-2-propanoate). 2 and derivatives were fully characterized by mass spectrometry and X-ray crystallography. Electron paramagnetic resonance spectroscopy and X-ray photoelectron spectroscopy confirm that the oxidation is metal-centered. 2 was found to react with a variety of phenolic and hydrocarbon substrates. A linear correlation between the measured rate constant and the substrate bond dissociation enthalpy (BDE) was found for both phenolic and hydrocarbon substrates. Large H/D kinetic isotope effects were also observed for both sets of substrates. These results suggest that 2 reacts through concerted proton-electron transfer (CPET). Analysis of measured thermodynamic parameters allows us to calculate a bond dissociation free energy (BDFE) of similar to 91 kcal mol(-1) for the O-H bond of the bound pyalk ligand. These findings may shed light onto CPET steps in oxidative catalysis and have implications for ligand design in catalytic systems.
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