School of Life and Environmental Sciences, Deakin University, Burwood, Victoria 3125, Australia.
Molecules. 2022 Nov 1;27(21):7428. doi: 10.3390/molecules27217428.
The oxidative electrochemistry of cymantrene, CpMn(CO) (; Cp = [η-CH]), was examined in ionic liquids (ILs) composed of anions of varying Lewis base properties. It was observed that the cyclic voltammetric responses strongly depended on the nucleophilic properties of the IL anion. Still, all observations are consistent with the initial formation of followed by an attack from the IL anion. In bis(trifluoromethylsulfonyl)amide [NTf]-based ILs, the process shows close to ideal electrochemical reversibility as the reaction between and [NTf] anion is very slow. On the other hand, in tetrafluoroborate and trifluoromethanesulfonate-based IL, the oxidation of shows different levels of electrochemical reversibility with a marked sign of anion attack to . In contrast, exhibits an irreversible oxidation process in hexafluorophosphate-based IL. The reaction rate constants for the interaction of with the different IL anions were estimated by fitting the experimental data to digital simulations of the proposed mechanism. Besides, the use of [NTf]-based ILs as a supporting electrolyte in CHCl was also examined. The oxidation process of shows a close to ideal electrochemical reversibility but low to non-chemical reversibility. This study illustrates the wide range of electrochemical environments available with ILs and demonstrates their limited utility for investigating the redox properties of metal carbonyl compounds. It also intends to warn the reader on how the IL media may influence an electrochemical study if care is not exercised.
金属茂钐（CpMn(CO)₅；Cp=[η-CH₅]）的氧化电化学在由不同路易斯碱性质的阴离子组成的离子液体（ILs）中进行了研究。观察到循环伏安响应强烈依赖于 IL 阴离子的亲核性质。尽管如此，所有观察结果都与初始形成[CpMn(CO)₅]+的形成一致，然后是 IL 阴离子的攻击。在双（三氟甲烷磺酰基）酰胺 [NTf] - 基 ILs 中，该过程表现出接近理想的电化学可逆性，因为 [CpMn(CO)₅]+与 [NTf] 阴离子之间的反应非常缓慢。另一方面，在四氟硼酸盐和三氟甲磺酸酯基 IL 中，[CpMn(CO)₅]+的氧化表现出不同程度的电化学可逆性，明显有阴离子攻击 [CpMn(CO)₅]+的迹象。相比之下，在六氟磷酸盐基 IL 中，[CpMn(CO)₅]+表现出不可逆的氧化过程。通过将实验数据拟合到所提出的机制的数字模拟，估计了 [CpMn(CO)₅]+与不同 IL 阴离子相互作用的反应速率常数。此外，还研究了在 CHCl 中使用 [NTf] - 基 IL 作为支持电解质的情况。[CpMn(CO)₅]+的氧化过程表现出接近理想的电化学可逆性，但低至非化学可逆性。这项研究说明了 ILs 提供的广泛电化学环境，并展示了它们在研究金属羰基化合物的氧化还原性质方面的有限用途。它还旨在警告读者，如果不注意，IL 介质可能会如何影响电化学研究。
