金属イオン共役電子移動による高原子価金属オキソ錯体の水の酸化触媒活性制御

我们报道了非血红素铁(IV)-氧配合物[(N4Py)Fe^<IV>(O)]^<2+>（N4Py = N， N-二（2-吡啶基甲基）-N-二（2-吡啶基）甲胺）与三氟酸（HOTf）的高效环氧化。[(N4Py)Fe^<IV>(O)]^<2+>（N4Py = N， N-二（2-吡啶基甲基）-N-二（2-吡啶基）甲胺）在298 K的乙腈中没有氧化苯乙烯衍生物，而苯乙烯衍生物通过质子耦合电子转移（PCET）从苯乙烯衍生物到[(N4Py)Fe^<IV>(O)]^<2+>的双质子化产物，苯乙烯衍生物的环氧化反应是可能的。当考虑前体配合物形成常数的差异时，根据Marcus电子转移理论，所有前体配合物中电子供体[(N4Py)Fe^<IV>(O)]^<2+>的苯乙烯衍生物和PCET在hotf促进下的一阶速率常数的对数与PCET的驱动力具有显著的统一相关性。在前驱体配合物中，hotf促进氧原子从硫代氨基酚转移到[(N4Py)Fe^<IV>(O)]^<2+>和hotf促进氢原子从甲苯衍生物转移到[(N4Py)Fe^<IV>(O)]^<2+>的一级速率常数具有相同的PCET驱动力依赖关系。因此，hotf促进苯乙烯衍生物被[(N4Py)Fe^<IV>(O)]^<2+>环氧化的过程是通过从苯乙烯衍生物到[(N4Py)Fe^<IV>(O)]^<2+>的速率电子转移进行的，如hotf促进氧原子从硫代异构转移到[(N4Py)Fe^<IV>(O)]^<2+>和hotf促进氢原子从甲苯衍生物转移到[(N4Py)Fe^<IV>(O)]^<2+>的情况。

We report efficient epoxidation of styrene derivatives by a nonheme iron(IV)-oxo complex, [(N4Py)Fe^<IV>(O)]^<2+>(N4Py = N, N-bis(2-pyridylmethyl)-N- bis(2-pyridyl)methylamine) with trilflic acid (HOTf). No oxidation of styrene derivatives by [(N4Py)Fe^<IV>(O)]^<2+>(N4Py = N, N-bis(2-pyridylmethyl)-N-bis(2-pyridyl) methylamine) occurred in acetonitrile at 298 K, whereas efficient epoxidation of styrene derivatives was made possible by the presence of triflic acid (HOTf) via proton-coupled electron transfer (PCET) from styrene derivatives to the diprotonated species of [(N4Py)Fe^<IV>(O)]^<2+> with HOTf. Logarithms of the first-order rate constants of HOTf-promoted expoxidation of all styrene derivatives with [(N4Py)Fe^<IV>(O)]^<2+> and PCET from electron donors in the precursor complexes exhibit a remarkably unified correlation with the driving force of PCET in light of the Marcus theory of electron transfer when the differences in the formation constants of precursor complexes are taken into account. The same PCET driving force dependence is obtained for the first-order rate constants of HOTf-promoted oxygen atom transfer from thioanisols to [(N4Py)Fe^<IV>(O)]^<2+> and HOTf-promoted hydrogen atom transfer from toluene derivatives to [(N4Py)Fe^<IV>(O)]^<2+> in the precursor complexes. Thus, HOTf-promoted epoxidation of styrene derivatives by [(N4Py)Fe^<IV>(O)]^<2+> proceeds via the rate-determining electron transfer from styrene derivatives to the diprotonated species of [(N4Py)Fe^<IV>(O)]^<2+> as the case of HOTf-promoted oxygen atom transfer from thioanisols to [(N4Py)Fe^<IV>(O)]^<2+> and HOTf-promoted hydrogen atom transfer from toluene derivatives to [(N4Py)Fe^<IV>(O)]^<2+>.