Department of Chemistry, Graduate School of Humanities and Sciences, Nara Women's University, Kitauoyanishi, Nara 630-8506, Japan.
Inorg Chem. 2021 Jul 5;60(13):9243-9247. doi: 10.1021/acs.inorgchem.1c01018. Epub 2021 Jun 14.
The solvent effect on the reactivity of high-valent metal oxo complexes has not been studied well, because of their solubility and stability. We synthesize oxoiron(IV) porphyrin π-cation radical complexes ( and ) having the -hexyl side chains. and are soluble in various solvents, even in hexane, at -80 °C, allowing for the study of their reactivity in various organic solvents. We show that pentane, hexane, heptane, and -butyl methyl ether significantly increase the reactivity of and , but dichloromethane, the most frequently used solvent in previous studies, is the worst for increasing the reactivity among the solvents. H NMR and EPR spectroscopies show no significant change in hexane, but the Eyring plots for the epoxidation reactions indicate that the entropies of activation in -alkane solvents are larger than those in dichloromethane. The observed solvent effect can be rationalized with reorganization energy of the solvent in the reaction.
溶剂对高价金属氧络合物反应性的影响尚未得到很好的研究,因为它们的溶解度和稳定性。我们合成了具有 - 己基侧链的氧代铁 (IV) 卟啉 π-阳离子自由基配合物(和)。和在各种溶剂中都具有可溶性,甚至在 -80°C 的正己烷中也具有可溶性,这使得可以在各种有机溶剂中研究它们的反应性。我们表明,戊烷、己烷、庚烷和 - 丁基甲基醚显著增加了和的反应性,但二氯甲烷是以前研究中最常用的溶剂,在增加反应性方面是最差的溶剂。H NMR 和 EPR 光谱表明在正己烷中没有明显变化,但环氧化反应的 Eyring 图表明,在 - 烷烃溶剂中的活化熵大于在二氯甲烷中的活化熵。观察到的溶剂效应可以用反应中溶剂的重组能来合理化。