Rates of Electron Self-Exchange Reactions between Oxo-Centered Ruthenium Clusters Are Determined by Orbital Overlap

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• 作者：John C. Goeltz ; Christina J. Hanson ; Clifford P. Kubiak
• 刊名：Inorganic Chemistry
• 出版年：2009
• 出版时间：June 1, 2009
• 年：2009
• 卷：48
• 期：11
• 页码：4763-4767
• 全文大小：925K
• 年卷期：v.48,no.11(June 1, 2009)
• ISSN：1520-510X

文摘

We report rate constants for electron self-exchange of trinuclear ruthenium clusters of the type [Ru₃O(OAc)₆(CO)(L)₂]^0/−, where L is 4-cyanopyridine, pyridine, or 4-(dimethylamino)pyridine. Rate constants were determined by ¹H NMR line-broadening experiments in CD₃CN, CD₂Cl₂, and THF-d₈, and range from 6.5 × 10⁶ to 2.5 × 10⁸ s⁻¹ M⁻¹. Faster self-exchange is observed with more electron-withdrawing substituents on the ancillary pyridine ligands. This effect is attributed to increased orbital overlap between the donor and acceptor as more electron density is drawn onto the pyridine ring. This view is supported by measured NMR contact shifts of the pyridyl protons which reflect increased electron spin density with increasing pyridine ligand electron-withdrawing ability. Normal solvent dependence is also observed, where higher outer-sphere reorganization energies lead to slower exchange.