Density Functional Theory Calculations on Oxidative CC Bond Cleavage and NO Bond Formation of [RuII(bpy)2(diamine)]2+ via Reactive Ruthenium Imide Intermediates. Issue 46 (29th September 2014)

• Record Type: Journal Article
• Authors: Guan, Xiangguo; Law, Siu‐Man; Tse, Chun‐Wai; Huang, Jie‐Sheng; Che, Chi‐Ming
• Is Part Of: Chemistry. Volume 20:Issue 46(2014)
• Page Start: 15122
• Page End: 15130
• Publication Date: 2014-09-29
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201402517
• Languages: English
• ISSNs: 0947-6539

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>DFT calculations are performed on [Ru<sup>II</sup>(bpy)<sub>2</sub>(tmen)]<sup>2+</sup> (<bold>M1</bold>, tmen=2, 3‐dimethyl‐2, 3‐butanediamine) and [Ru<sup>II</sup>(bpy)<sub>2</sub>(heda)]<sup>2+</sup> (<bold>M2</bold>, heda=2, 5‐dimethyl‐2, 5‐hexanediamine), and on the oxidation reactions of <bold>M1</bold> to give the CC bond cleavage product [Ru<sup>II</sup>(bpy)<sub>2</sub>(NH=CMe<sub>2</sub>)<sub>2</sub>]<sup>2+</sup> (<bold>M3</bold>) and the NO bond formation product [Ru<sup>II</sup>(bpy)<sub>2</sub>(ONCMe<sub>2</sub>CMe<sub>2</sub>NO)]<sup>2+</sup> (<bold>M4</bold>). The calculated geometrical parameters and oxidation potentials are in good agreement with the experimental data. As revealed by the DFT calculations, [Ru<sup>II</sup>(bpy)<sub>2</sub>(tmen)]<sup>2+</sup> (<bold>M1</bold>) can undergo oxidative deprotonation to generate Ru‐bis(imide) [Ru(bpy)<sub>2</sub>(tmen‐4 H)]<sup>+</sup> (<bold>A</bold>) or Ru‐imide/amide [Ru(bpy)<sub>2</sub>(tmen‐3 H)]<sup>2+</sup> (<bold>A′</bold>) intermediates. Both <bold>A</bold> and <bold>A′</bold> are prone to CC bond cleavage, with low reaction barriers (Δ<italic>G</italic><sup>≠</sup>) of 6.8 and 2.9 kcal mol<sup>−1</sup> for their doublet spin states <sup><bold>2</bold></sup><bold>A</bold> and <sup><bold>2</bold></sup><bold>A′</bold>, respectively. The calculated reaction barrier for the nucleophilic attack of water molecules on <sup><bold>2</bold></sup><bold>A′</bold> is relatively high (14.2 kcal mol<sup>−1</sup>). These calculation results are in agreement with the formation of the Ru<sup>II</sup>‐bis(imine) complex <bold>M3</bold> from the electrochemical oxidation of <bold>M1</bold> in aqueous solution. The oxidation of <bold>M1</bold> with Ce<sup>IV</sup> in aqueous solution to afford the Ru<sup>II</sup>‐dinitrosoalkane complex <bold>M4</bold> 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.</p> </abstract>