Density Functional Theory Calculations on Oxidative CC Bond Cleavage and NO Bond Formation of [RuII(bpy)2(diamine)]2+ via Reactive Ruthenium Imide Intermediates |
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| Authors: | Dr Xiangguo Guan Siu‐Man Law Chun‐Wai Tse Dr Jie‐Sheng Huang Prof?Dr Chi‐Ming Che |
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| Institution: | 1. Department of Chemistry and State Key Laboratory of Synthetic Chemistry, The University of Hong Kong, Pokfulam Road (Hong Kong), Fax: (+852)?2857‐1586;2. HKU Shenzhen Institute of Research and Innovation, Shenzhen 518053 (P. R. China) |
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| Abstract: | DFT calculations are performed on RuII(bpy)2(tmen)]2+ ( M1 , tmen=2,3‐dimethyl‐2,3‐butanediamine) and RuII(bpy)2(heda)]2+ ( M2 , heda=2,5‐dimethyl‐2,5‐hexanediamine), and on the oxidation reactions of M1 to give the C?C bond cleavage product RuII(bpy)2(NH=CMe2)2]2+ ( M3 ) and the N?O bond formation product RuII(bpy)2(ONCMe2CMe2NO)]2+ ( M4 ). The calculated geometrical parameters and oxidation potentials are in good agreement with the experimental data. As revealed by the DFT calculations, RuII(bpy)2(tmen)]2+ ( M1 ) can undergo oxidative deprotonation to generate Ru‐bis(imide) Ru(bpy)2(tmen‐4 H)]+ ( A ) or Ru‐imide/amide Ru(bpy)2(tmen‐3 H)]2+ ( A′ ) intermediates. Both A and A′ are prone to C?C bond cleavage, with low reaction barriers (ΔG≠) of 6.8 and 2.9 kcal mol?1 for their doublet spin states 2 A and 2 A′ , respectively. The calculated reaction barrier for the nucleophilic attack of water molecules on 2 A′ is relatively high (14.2 kcal mol?1). These calculation results are in agreement with the formation of the RuII‐bis(imine) complex M3 from the electrochemical oxidation of M1 in aqueous solution. The oxidation of M1 with CeIV in aqueous solution to afford the RuII‐dinitrosoalkane complex M4 is proposed to proceed by attack of the cerium oxidant on the ruthenium imide intermediate. The findings of ESI‐MS experiments are consistent with the generation of a ruthenium imide intermediate in the course of the oxidation. |
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| Keywords: | C C bond cleavage density functional calculations N O bond formation reaction mechanisms reduction potentials ruthenium imide complexes |
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