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

本文报道了非血红素铁（IV）-氧代配合物[（N4 Py）Fe^<IV>（O）]^&lt;2+&gt;（N4 Py = N，N-双（2-吡啶基甲基）-N-双（2-吡啶基）甲胺）与三氟甲磺酸（HOTf）的有效环氧化苯乙烯衍生物。在298 K乙腈中，[（N4 Py）Fe^<IV>（O）]^2+（N4 Py = N，N-双（2-吡啶基甲基）-N-双（2-吡啶基）甲胺）不氧化苯乙烯衍生物，而在三氟甲磺酸（HOTf）存在下，通过质子耦合电子转移（PCET）从苯乙烯衍生物到[（N4 Py）Fe^（O）]^2+与HOTf的双质子化物种，苯乙烯衍生物的有效环氧化成为可能<IV>。HOTf促进的所有苯乙烯衍生物与[（N4 Py）Fe^<IV>（O）]^2+和PCET的双氧化反应的一级速率常数的对数值，在考虑前体络合物形成常数差异的情况下，与Marcus电子转移理论中的PCET驱动力呈现出明显统一的相关性.在前体配合物中，HOTf促进的氧原子从茴香硫醚转移到[（N4 Py）Fe^<IV>（O）]^&lt;2+&gt;和HOTf促进的氢原子从甲苯衍生物转移到[（N4 Py）Fe^<IV>（O）]^&lt;2+&gt;的一级速率常数获得了相同的PCET驱动力依赖性。因此，HOTf促进的苯乙烯衍生物通过[（N4 Py）Fe^<IV>（O）]^&lt;2+&gt;的环氧化通过从苯乙烯衍生物到[（N4 Py）Fe^<IV>（O）]^&lt;2+&gt;的双质子化物种的速率决定电子转移进行，就像HOTf促进的氧原子从茴香硫醚转移到[（N4 Py）Fe^<IV>（O）]^&lt;2+&gt;和HOTf促进的氢原子从甲苯衍生物转移到[（N4 Py）Fe^<IV>（O）]^&lt;2+&gt;的情况一样。

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+>.