A Highly Oxidizing and Isolable Oxoruthenium(V) Complex [Ru V (N 4 O)(O)] 2+ : Electronic Structure, Redox Properties, and Oxidation Reactions Investigated by DFT Calculations

The electronic structure and redox properties of the highly oxidizing, isolable Ru V O complex [Ru V (N 4 O)(O)] 2+ , 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 (Δ G ≠ =25.5 kcal mol −1 ) of oxidation of hydrochloric acid can be decomposed into two parts: the formation of [Ru III (N 4 O)(HOCl)] 2+ (Δ G =15.0 kcal mol −1 ) and the substitution of HOCl by a water molecule (Δ G ≠ =10.5 kcal mol −1 ). For water oxidation, nucleophilic attack on Ru V O by water, leading to OO bond formation, has a free energy barrier of 24.0 kcal mol −1 , the major component of which comes from the cleavage of the HOH bond of water. Intermolecular self‐coupling of two molecules of [Ru V (N 4 O)(O)] 2+ leads to the [(N 4 O)Ru IV O 2 Ru III (N 4 O)] 4+ complex with a calculated free energy barrier of 12.0 kcal mol −1 .