An MO-theoretical Approach to the Aquation Mechanism of Carboxylatopentaammineruthenium(III) Complexes in Acid Solutions

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概要

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• The aquation mechanism of carboxylatopentaammineruthenium(III) complexes, (NH<SUB>3</SUB>)<SUB>5</SUB>RuO<SUB>2</SUB>CR<SUP>2+</SUP>, where R=H, CH<SUB>3</SUB>, C<SUB>2</SUB>H<SUB>5</SUB>, (CH<SUB>3</SUB>)<SUB>2</SUB>CH, and CH<SUB>2</SUB>OH, has been investigated with the Wolfsberg-Helmholz-LCAO-MO extended Hückel method augmented by metal d-orbitals. The very weak Ru–O coordination linkage (bond population=0.085–0.092) formed mainly by the antibonding d<SUB>z</SUB>2p<SUB>z</SUB>-σ and p<SUB>z</SUB>p<SUB>z</SUB>-σ orbitals facilitates the heterolytic bond-breaking of the Ru–O(dissociation energy=4.61–9.22 kcal/mol), and the order of the bond populations of the Ru–O is well reflected in that of the overall aquation rates.The preferable structure of the protonated complex is (NH<SUB>3</SUB>)<SUB>5</SUB>RuOHG(=O)R<SUP>2+</SUP>, produced by the interaction between the H<SUP>+</SUP> catalyst and the non-bonding lonepair orbital of the neighboring oxygen atom attached to the metal.The H<SUB>2</SUB>O solvent was found to play an important role in the bond dissociation of the metal-oxygen linkage from a linear dependence between the reactivity index (1/2<I>N</I><SUB>z<SUP>2</SUP></SUB><SUP>LU</SUP>) of the protonated complex to such nucleophiles as H<SUB>2</SUB>O and the activation energy for the S<SUB>N</SUB>2 aquation reaction. The proposed tetragonal pyramidal intermediate of (NH<SUB>3</SUB>)<SUB>5</SUB>Ru<SUP>3+</SUP> combines easily the Ru–O through the lowest unoccupied <I>d</I><SUB>z<SUP>2</SUP></SUB> Ru-orbital, forming an aquo-complex with the binding energy of with H<SUB>2</SUB>O linkage, 30.25 kcal/mol

• 公益社団法人 日本化学会の論文

著者

• Sakamoto Hiroyuki

  Faculty of Engineering, Kumamoto University

• Kitagawa Futoshi

  Faculty of Engineering, Kumamoto University

• Ohyoshi Akira

  Faculty of Engineering, Kumamoto University

• Ohkubo Kastutoshi

  Faculty of Engineering, Kumamoto University

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• Simulation Analysis of the Acid–catalyzed Hydrolysis of Carboxylatopentammineruthenium(III) Complexes
• An MO-theoretical Approach to the Aquation Mechanism of Carboxylatopentaammineruthenium(III) Complexes in Acid Solutions

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