Analysis of Hydrogen Atom Abstraction from Ethylbenzene by an (FeO)-O-V(TAML) Complex

作者：Shen Longzhu Q; Kundu Soumen; Collins Terrence J; Bominaar Emile L^*

来源：Inorganic Chemistry, 2017, 56(8): 4347-4356.

DOI：10.1021/acs.inorgchem.6b02796

It was shown previously (Chem. Eur. J. 2015, 21, 1803) that the rate of hydrogen atom abstraction, k, from ethylbenzene (EB) by TAML complex [Fe-v(O)B*](-) (1) in acetonitrile exhibits a large kinetic isotope effect (KIE similar to 26) in the experimental range 233-243 K. The extrapolated tangents of ln(k/T) vs T-1 plots for EB-d(10) and EB gave a large, negative intercept difference, Int(EB) - Int(EB-d(10)) = -34.5 J mol(-1) K-1 for T-1 -> 0, which is shown to be exclusively due to an isotopic mass effect on tunneling. A decomposition of the apparent activation barrier in terms of electronic, ZPE, thermal enthalpic, tunneling, and entropic contributions is presented. Tunneling corrections to Delta H-double dagger and Delta S-double dagger are estimated to be large. The DFT prediction, using functional B3LYP and basis set 6-311G, for the electronic contribution is significantly smaller than suggested by experiment. However, the agreement improves after correction for the basis set superposition error in the interaction between EB and 1. The kinetic model employed has been used to predict rate constants outside the experimental temperature range, which enabled us to compare the reactivity of 1 with those of other hydrogen abstracting complexes.

• 出版日期2017-4-17