State Key Laboratory of Synthetic Chemistry, Institute of Molecular Functional Materials, and Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, PR China.
Chem Asian J. 2013 Sep;8(9):2046-56. doi: 10.1002/asia.201300458. Epub 2013 Jun 20.
The electronic structure and redox properties of the highly oxidizing, isolable Ru(V)=O complex Ru(V)(N4O)(O), its oxidation reactions with saturated alkanes (cyclohexane and methane) and inorganic substrates (hydrochloric acid and water), and its intermolecular coupling reaction have been examined by DFT calculations. The oxidation reactions with cyclohexane and methane proceed through hydrogen atom transfer in a transition state with a calculated free energy barrier of 10.8 and 23.8 kcal mol(-1), respectively. The overall free energy activation barrier (ΔG(≠)=25.5 kcal mol(-1)) of oxidation of hydrochloric acid can be decomposed into two parts: the formation of Ru(III)(N4O)(HOCl) (ΔG=15.0 kcal mol(-1)) and the substitution of HOCl by a water molecule (ΔG(≠)=10.5 kcal mol(-1)). For water oxidation, nucleophilic attack on Ru(V)=O by water, leading to O-O bond formation, has a free energy barrier of 24.0 kcal mol(-1), the major component of which comes from the cleavage of the H-OH bond of water. Intermolecular self-coupling of two molecules of Ru(V)(N4O)(O) leads to the (N4O)Ru(IV)-O2-Ru(III)(N4O) complex with a calculated free energy barrier of 12.0 kcal mol(-1).
通过密度泛函理论（DFT）计算研究了强氧化性、可分离的 Ru(V)=O 配合物 Ru(V)(N4O)(O) 的电子结构和氧化还原性质，及其与饱和烷烃（环己烷和甲烷）及无机底物（盐酸和水）的氧化反应，以及其分子间偶联反应。与环己烷和甲烷的氧化反应通过过渡态中的氢原子转移进行，计算得到的自由能势垒分别为 10.8 和 23.8 kcal/mol。盐酸氧化的总自由能活化势垒（ΔG(≠)=25.5 kcal/mol）可分解为两部分：Ru(III)(N4O)(HOCl) 的形成（ΔG=15.0 kcal/mol）和水分子取代 HOCl（ΔG(≠)=10.5 kcal/mol）。对于水氧化，水分子对 Ru(V)=O 的亲核攻击导致 O-O 键形成，其自由能势垒为 24.0 kcal/mol，主要来自水分子中 H-OH 键的断裂。两个 Ru(V)(N4O)(O) 分子的分子间自偶联导致 (N4O)Ru(IV)-O2-Ru(III)(N4O) 配合物的形成，其计算得到的自由能势垒为 12.0 kcal/mol。
