Dey Sanchaita, Panda Sanjib, Ghosh Prabir, Lahiri Goutam Kumar
Department of Chemistry , Indian Institute of Technology Bombay , Powai, Mumbai 400076 , India.
Inorg Chem. 2019 Jan 22;58(2):1627-1637. doi: 10.1021/acs.inorgchem.8b03191. Epub 2019 Jan 7.
This work evaluated the switchable binding profile of the biochemically relevant and redox non-innocent C-organonitroso (ArNO) moiety with the selective {Ru(acac)} (acac = acetylacetonate) metal fragment as a function of external stimuli, including the solvent medium (EtOH versus toluene) and aryl substituents (CH, p-OMe-CH, and p-Cl-CH) in the framework of ArNO. In this context, the reaction of ArNO (Ar = CH or p-OMe-CH) with the metal precursor Ru(acac)(CHCN) in polar protic EtOH led to the formation of monomeric [Ru(acac)(ArNO)] (1a or 1b) with η-N-bonded terminal ArNO and double-ArNO-bridged dimeric [(acac)Ru(μ-ArNO)Ru(acac)], 2a or 2b, respectively. On the other hand, the use of p-Cl-substituted ArNO selectively yielded the corresponding dimeric 2c. However, the use of nonpolar toluene resulted in monomeric 1 irrespective of the nature of aryl substituents in ArNO. Molecular identities, including the redox state of ArNO in 1 and 2, were authenticated by their single-crystal X-ray structures as well as by solution spectral features. Though monomeric 1 exhibited reversible one-electron oxidation and reduction processes, leading to the electron paramagnetic resonance active [Ru(acac)(ArNO)] (1; S = /) and [Ru(acac)(ArNO)(ArNO)] (1; S = /), respectively, redox states of dimeric 2 were found to be unstable on the electrolysis time scale. Interestingly, monomeric 1 underwent transformation to dimeric 2 in the presence of a strong reducing agent, hydrazine hydrate, and the reverse process, i.e., conversion of dimeric 2 to 1, took place under the influence of external coordinating agent ArNO. The detailed experimental exploration, including kinetic investigations related to 1 → 2 and 2 → 1 transformations, revealed that the electronic aspects of ArNO (redox non-innocence of ArNO, π-accepting and coordinating features of ArNO) had facilitated its switchable binding event in combination with the {Ru(acac)} metal fragment.
本工作评估了具有生化相关性且氧化还原非惰性的碳有机亚硝基（ArNO）部分与选择性的{Ru(acac)}（acac = 乙酰丙酮）金属片段的可切换结合模式，该模式是外部刺激的函数，外部刺激包括溶剂介质（乙醇与甲苯）以及ArNO框架中的芳基取代基（CH、对甲氧基-CH和对氯-CH）。在此背景下，ArNO（Ar = CH或对甲氧基-CH）与金属前体Ru(acac)(CHCN)在极性质子溶剂乙醇中反应，分别生成具有η-N键合末端ArNO的单体[Ru(acac)(ArNO)]（1a或1b）和双ArNO桥联二聚体[(acac)Ru(μ-ArNO)Ru(acac)]，即2a或2b。另一方面，使用对氯取代的ArNO选择性地生成相应的二聚体2c。然而，使用非极性甲苯时，无论ArNO中芳基取代基的性质如何，都会生成单体1。通过单晶X射线结构以及溶液光谱特征验证了包括1和2中ArNO的氧化还原状态在内的分子结构。尽管单体1表现出可逆的单电子氧化和还原过程，分别生成电子顺磁共振活性的[Ru(acac)(ArNO)]（1；S = 1/2）和[Ru(acac)(ArNO)(ArNO)]（1；S = 1/2），但发现二聚体2的氧化还原状态在电解时间尺度上不稳定。有趣的是，单体1在强还原剂水合肼存在下会转化为二聚体2，而相反的过程，即二聚体2转化为1，则在外部配位剂ArNO的影响下发生。详细的实验探索，包括与1→2和2→1转化相关的动力学研究，表明ArNO的电子特性（ArNO的氧化还原非惰性、ArNO的π-接受和配位特性）与{Ru(acac)}金属片段相结合促进了其可切换的结合事件。
