Precise investigation of the axial ligand substitution mechanism on a hydrogenphosphato-bridged lantern-type platinum(III) binuclear complex in acidic aqueous solution

Satoshi Iwatsuki, Chiho Mizushima, Naoyuki Morimoto, Shinji Muranaka, Koji Ishihara, Kazuko Matsumoto

    Research output: Contribution to journalArticle

    15 Citations (Scopus)

    Abstract

    Detailed equilibrium and kinetic studies on axial water ligand substitution reactions of the "lantern-type" platinum-(III) binuclear complex, [Pt 2(μ-HPO 4) 4(H 2O) 2] 2-, with halide and pseudo-halide ions (X - = Cl -, Br -, and SCN -) were carried out in acidic aqueous solution at 25°C with I = 1.0 M. The diaqua Pt(III) dimer complex is in acid dissociation equilibrium in aqueous solution with -log K h1 = 2.69 ± 0.04. The consecutive formation constants of the aquahalo complex (K 1 X) and the dihalo complex (K 2 X) were determined spectrophotometrically to be log K 1 Cl = 2.36 ± 0.01 and log K 2 Cl = 1.47 ± 0.01 for the reaction with Cl - and log K 1 Br = 2.90 ± 0.04 and log K 2 Br = 2.28 ± 0.01 for the reaction with Br -, respectively. In the kinetic measurements carried out under the pseudo-first-order conditions with a large excess concentration of halide ion compared to that of Pt(III) dimer (C X- ≫ C Pt), all of the reactions proceeded via a one-step first-order reaction, which is a contrast to the consecutive two-step reaction for the amidato-bridged platinum(III) binuclear complexes. The conditional first-order rate constant (k obs) depended on C X- as well as the acidity of the solution. From kinetic analyses, the rate-limiting step was determined to be the first substitution process that forms the monohalo species, which is in rapid equilibrium with the dihalo complex. The reaction with 4-penten-1-ol was also kinetically investigated to examine the reactivity of the lantern complex with olefin compounds.

    Original languageEnglish
    Pages (from-to)8097-8104
    Number of pages8
    JournalInorganic Chemistry
    Volume44
    Issue number22
    DOIs
    Publication statusPublished - 2005 Oct 31

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    Platinum
    platinum
    Substitution reactions
    substitutes
    Ligands
    aqueous solutions
    Dimers
    ligands
    Kinetics
    Ions
    halides
    Alkenes
    Acidity
    Rate constants
    kinetics
    dimers
    Acids
    Water
    acidity
    alkenes

    ASJC Scopus subject areas

    • Inorganic Chemistry

    Cite this

    Precise investigation of the axial ligand substitution mechanism on a hydrogenphosphato-bridged lantern-type platinum(III) binuclear complex in acidic aqueous solution. / Iwatsuki, Satoshi; Mizushima, Chiho; Morimoto, Naoyuki; Muranaka, Shinji; Ishihara, Koji; Matsumoto, Kazuko.

    In: Inorganic Chemistry, Vol. 44, No. 22, 31.10.2005, p. 8097-8104.

    Research output: Contribution to journalArticle

    Iwatsuki, Satoshi ; Mizushima, Chiho ; Morimoto, Naoyuki ; Muranaka, Shinji ; Ishihara, Koji ; Matsumoto, Kazuko. / Precise investigation of the axial ligand substitution mechanism on a hydrogenphosphato-bridged lantern-type platinum(III) binuclear complex in acidic aqueous solution. In: Inorganic Chemistry. 2005 ; Vol. 44, No. 22. pp. 8097-8104.
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    AU - Iwatsuki, Satoshi

    AU - Mizushima, Chiho

    AU - Morimoto, Naoyuki

    AU - Muranaka, Shinji

    AU - Ishihara, Koji

    AU - Matsumoto, Kazuko

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    AB - Detailed equilibrium and kinetic studies on axial water ligand substitution reactions of the "lantern-type" platinum-(III) binuclear complex, [Pt 2(μ-HPO 4) 4(H 2O) 2] 2-, with halide and pseudo-halide ions (X - = Cl -, Br -, and SCN -) were carried out in acidic aqueous solution at 25°C with I = 1.0 M. The diaqua Pt(III) dimer complex is in acid dissociation equilibrium in aqueous solution with -log K h1 = 2.69 ± 0.04. The consecutive formation constants of the aquahalo complex (K 1 X) and the dihalo complex (K 2 X) were determined spectrophotometrically to be log K 1 Cl = 2.36 ± 0.01 and log K 2 Cl = 1.47 ± 0.01 for the reaction with Cl - and log K 1 Br = 2.90 ± 0.04 and log K 2 Br = 2.28 ± 0.01 for the reaction with Br -, respectively. In the kinetic measurements carried out under the pseudo-first-order conditions with a large excess concentration of halide ion compared to that of Pt(III) dimer (C X- ≫ C Pt), all of the reactions proceeded via a one-step first-order reaction, which is a contrast to the consecutive two-step reaction for the amidato-bridged platinum(III) binuclear complexes. The conditional first-order rate constant (k obs) depended on C X- as well as the acidity of the solution. From kinetic analyses, the rate-limiting step was determined to be the first substitution process that forms the monohalo species, which is in rapid equilibrium with the dihalo complex. The reaction with 4-penten-1-ol was also kinetically investigated to examine the reactivity of the lantern complex with olefin compounds.

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