Formation kinetics of peroxovanadium(V) complexes in strongly acidic media as studied by a high-pressure stopped-flow technique

Shigenobu Funahashi, Koji Ishihara, Masahiko Inamo, Motoharu Tanaka

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15 Citations (Scopus)

Abstract

A high-pressure stopped-flow vessel was made of acid-proof tantalum block which enabled us to follow reactions of vanadium(V) ion with hydrogen peroxide in strongly acidic media. The rate for the formation of the monoperoxo complex (VO(O2)+) is expressed as d [VO(O2)+]/dt = (k1[H+]-1 + k2 + k3 [H+])[VO2+]- [H2O2] where k1 (s-1) (25 °C)=60.2 [ΔH (kJ mol-1 = 21.1 ± 2.6, ΔS (J mol-1 K-1) = - 140 ± 9, ΔV (cm3 mol-1) = 9.9 ± 1.7], k2 (mo1-1 dm3 s-1) (25 °C) = 3.47 × 103 [ΔH = 46.5 ± 1.3, ΔS = -21 ±4, ΔV = 2.8 ± 1.0] and k3 (mol-2 dm6 s-1) (25 °C) = 1.63 × 103 [ΔH = 20.1 ± 4.7, Δ [tl]S = -116 ± 16, ΔV = 14.2 ± 3.2]. The rates of formation and dissociation of the diperoxo complex are described as d [VO(O2)2-]/dt = kf [VO(O2)+] [H2O2] and - d [VO(O2)2-]/dt = kd [VO(O2)2-] [H+]2, respectively, where kf (mol-1 dm3 s-1) (25 °C) = 3.49 × 103 [ΔH (kJ mol-1) = 40.2 ± 0.8, ΔS (J mol-1 K-1) = -42±3, ΔV (cm3 mol-1) =0.0±0.2]. and kd (mol-2 dm6 s-1) (25 °C) = 3.79 × 103 [ΔH = 45.7 ± 1.7, ΔS≠ = -23 ∓ 6]. Positive volumes of activation for the monoperoxo complex formation have been attributed to an expanded transition state with the distorted pentagonal-bipyramidal structure.

Original languageEnglish
Pages (from-to)65-71
Number of pages7
JournalInorganica Chimica Acta
Volume157
Issue number1
DOIs
Publication statusPublished - 1989 Mar 1
Externally publishedYes

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry
  • Materials Chemistry

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