Nitrosyl-Centered Redox and Acid–Base Interconversions in [Ru(Me3[9]aneN3)(bpy)(NO)]3,2,1+. The pKa of HNO for its Nitroxyl Derivative in Aqueous Sol

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• 作者：Nicolás Osa Codesido ; Thomas Weyhermüller ; José A. Olabe ; Leonardo D. Slep
• 刊名：Inorganic Chemistry
• 出版年：2014
• 出版时间：January 21, 2014
• 年：2014
• 卷：53
• 期：2
• 页码：981-997
• 全文大小：802K
• ISSN：1520-510X

文摘

This work reports the preparation of a new 6-coordinated nitrosyl compound and its use as a model to explore the redox and acid鈥揵ase properties of the three redox states of bound nitrosyl (formally NO⁺, NO^{鈥?/sup>, NO鈥?/sup>/HNO) in {RuNO}6,7,8 species. We prepared the octahedral {RuNO}6 complex [Ru(Me₃[9]aneN₃)(bpy)(NO)]3+ (Me₃[9]aneN₃: 1,4,7-trimethyl-1,4,7-triazacyclononane; bpy = 2,2鈥?bipyridine), and the related [Ru(Me₃[9]aneN₃)(bpy)(NO₂)]+ nitro derivative. The compounds were characterized by chemical analysis, X-ray diffraction, NMR, IR, and UV鈥搗is spectroscopies, cyclic voltammetry (CV), UV鈥搗is/IR spectroelectrochemistry, and theoretical calculations (DFT, (TD)DFT). The reaction kinetics between the {RuNO}6 complex and the nucleophile OH鈥?/sup> is also presented. The incorporation of tridentate and bidentate ligands in the coordination sphere prevents labilization issues associated with the trans effect when attaining the reduced states of the nitrosyl group. This allows for a consistent interpretation of the changes in the main geometrical parameters: Ru鈥揘 and N鈥揙 distances, Ru鈥揘鈥揙 angle, and the 谓_NO frequency and electronic transitions. We explore the redox properties in acetonitrile and aqueous solutions, and provide a potential (E_1/2) 鈭?pH (Pourbaix) diagram for the three diatomic nitrosyl-bound species, as well as for HNO and NO₂鈥?/sup>, including the report of the pK_a of the [Ru(Me₃[9]aneN₃)(bpy)(HNO)]2+ ion, 9.78 卤 0.15 at 25.0 掳C.}