Kinetics and mechanisms of the axial ligand substitution reaction of the head-to-head 2-pyridonato-bridged cis-Diammineplatinum(III) dinuclear complex

N. Saeki, Y. Hirano, Y. Sasamoto, I. Sato, T. Toshida, S. Ito, N. Nakamura, Koji Ishihara, K. Matsumoto

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    Abstract

    The following successive axial ligand substitution reactions of the head-to-head (HH) 2-pyridonato-bridged cis-diammineplatium(III) dinuclear complex ([(H2O)Pt(NH3)2(μ-C5H 4NO)2Pt(NH3)2(H2O)] 4+) with halide ions X- (X- = Cl- and Br-) to give monohalogeno and dihalogeno complexes were studied kinetically: [(H2O)Pt(NH3)2(μC5H 4NO)2Pt(NH3)2 (H2O)]4+ + X-Kobs1 [(H2O)Pt(NH3)2(μ-C5H 4NO)2Pt(NH3)2(X)]3+ + H2O, [(H2O)Pt(NH3)2(μ-C5H 4NO)2Pt(NH3)2(X)]2 (X)]3+ + X-Kobs2 [(X)Pt(NH3)2(μ-C5H4NO) 2Pt(NH3)2(X)]2+ +H2O. The acid dissociation constant (Kh1) of the axial aqua ligand in the HH dimer and the formation constants (K1 X and K2X of the monohalogeno and dihalogeno complexes were determined spectrophotometrically to be -log(Kh1/M) = 1.71 ± 0.04; log(K1 Cl/M-1) = 5.93 ± 0.02, log(K2 Cl/M-1) = 3.71 ± 0.00 for the reaction with Cl- and log(K1 Br/M-1) = 6.20 ± 0.05, log(K2 Br/M-1) = 4.55 ± 0.01 for the reaction with Br-. The two platinum atoms are nonequivalent in the HH dimer, in which the first deprotonation occurs selectively to the water molecule on the Pt(N4) atom and the first nucleophilic substitution with X- occurs preferentially to the Pt(N2O2) atom, where the atoms in parentheses are the coordinating atoms. The first water substitution with X- proceeds via two similar substitution paths, whereas the second substitution proceeds through two dissimilar paths: one is a simple substitution path and the other is via dissociation of the water molecule, providing a coordinatively unsaturated complex. These reaction paths are reasonably explained by the relative strength of the trans effect of the water, hydroxide, and halide ions in the monohalogeno complexes.

    Original languageEnglish
    Pages (from-to)861-868
    Number of pages8
    JournalBulletin of the Chemical Society of Japan
    Volume74
    Issue number5
    DOIs
    Publication statusPublished - 2001 May

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    Substitution reactions
    Ligands
    Kinetics
    Atoms
    Water
    Dimers
    Ions
    Deprotonation
    Molecules
    Platinum
    Acids

    ASJC Scopus subject areas

    • Chemistry(all)

    Cite this

    Kinetics and mechanisms of the axial ligand substitution reaction of the head-to-head 2-pyridonato-bridged cis-Diammineplatinum(III) dinuclear complex. / Saeki, N.; Hirano, Y.; Sasamoto, Y.; Sato, I.; Toshida, T.; Ito, S.; Nakamura, N.; Ishihara, Koji; Matsumoto, K.

    In: Bulletin of the Chemical Society of Japan, Vol. 74, No. 5, 05.2001, p. 861-868.

    Research output: Contribution to journalArticle

    Saeki, N. ; Hirano, Y. ; Sasamoto, Y. ; Sato, I. ; Toshida, T. ; Ito, S. ; Nakamura, N. ; Ishihara, Koji ; Matsumoto, K. / Kinetics and mechanisms of the axial ligand substitution reaction of the head-to-head 2-pyridonato-bridged cis-Diammineplatinum(III) dinuclear complex. In: Bulletin of the Chemical Society of Japan. 2001 ; Vol. 74, No. 5. pp. 861-868.
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    title = "Kinetics and mechanisms of the axial ligand substitution reaction of the head-to-head 2-pyridonato-bridged cis-Diammineplatinum(III) dinuclear complex",
    abstract = "The following successive axial ligand substitution reactions of the head-to-head (HH) 2-pyridonato-bridged cis-diammineplatium(III) dinuclear complex ([(H2O)Pt(NH3)2(μ-C5H 4NO)2Pt(NH3)2(H2O)] 4+) with halide ions X- (X- = Cl- and Br-) to give monohalogeno and dihalogeno complexes were studied kinetically: [(H2O)Pt(NH3)2(μC5H 4NO)2Pt(NH3)2 (H2O)]4+ + X- ⇄ Kobs1 [(H2O)Pt(NH3)2(μ-C5H 4NO)2Pt(NH3)2(X)]3+ + H2O, [(H2O)Pt(NH3)2(μ-C5H 4NO)2Pt(NH3)2(X)]2 (X)]3+ + X- ⇄ Kobs2 [(X)Pt(NH3)2(μ-C5H4NO) 2Pt(NH3)2(X)]2+ +H2O. The acid dissociation constant (Kh1) of the axial aqua ligand in the HH dimer and the formation constants (K1 X and K2X of the monohalogeno and dihalogeno complexes were determined spectrophotometrically to be -log(Kh1/M) = 1.71 ± 0.04; log(K1 Cl/M-1) = 5.93 ± 0.02, log(K2 Cl/M-1) = 3.71 ± 0.00 for the reaction with Cl- and log(K1 Br/M-1) = 6.20 ± 0.05, log(K2 Br/M-1) = 4.55 ± 0.01 for the reaction with Br-. The two platinum atoms are nonequivalent in the HH dimer, in which the first deprotonation occurs selectively to the water molecule on the Pt(N4) atom and the first nucleophilic substitution with X- occurs preferentially to the Pt(N2O2) atom, where the atoms in parentheses are the coordinating atoms. The first water substitution with X- proceeds via two similar substitution paths, whereas the second substitution proceeds through two dissimilar paths: one is a simple substitution path and the other is via dissociation of the water molecule, providing a coordinatively unsaturated complex. These reaction paths are reasonably explained by the relative strength of the trans effect of the water, hydroxide, and halide ions in the monohalogeno complexes.",
    author = "N. Saeki and Y. Hirano and Y. Sasamoto and I. Sato and T. Toshida and S. Ito and N. Nakamura and Koji Ishihara and K. Matsumoto",
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    T1 - Kinetics and mechanisms of the axial ligand substitution reaction of the head-to-head 2-pyridonato-bridged cis-Diammineplatinum(III) dinuclear complex

    AU - Saeki, N.

    AU - Hirano, Y.

    AU - Sasamoto, Y.

    AU - Sato, I.

    AU - Toshida, T.

    AU - Ito, S.

    AU - Nakamura, N.

    AU - Ishihara, Koji

    AU - Matsumoto, K.

    PY - 2001/5

    Y1 - 2001/5

    N2 - The following successive axial ligand substitution reactions of the head-to-head (HH) 2-pyridonato-bridged cis-diammineplatium(III) dinuclear complex ([(H2O)Pt(NH3)2(μ-C5H 4NO)2Pt(NH3)2(H2O)] 4+) with halide ions X- (X- = Cl- and Br-) to give monohalogeno and dihalogeno complexes were studied kinetically: [(H2O)Pt(NH3)2(μC5H 4NO)2Pt(NH3)2 (H2O)]4+ + X- ⇄ Kobs1 [(H2O)Pt(NH3)2(μ-C5H 4NO)2Pt(NH3)2(X)]3+ + H2O, [(H2O)Pt(NH3)2(μ-C5H 4NO)2Pt(NH3)2(X)]2 (X)]3+ + X- ⇄ Kobs2 [(X)Pt(NH3)2(μ-C5H4NO) 2Pt(NH3)2(X)]2+ +H2O. The acid dissociation constant (Kh1) of the axial aqua ligand in the HH dimer and the formation constants (K1 X and K2X of the monohalogeno and dihalogeno complexes were determined spectrophotometrically to be -log(Kh1/M) = 1.71 ± 0.04; log(K1 Cl/M-1) = 5.93 ± 0.02, log(K2 Cl/M-1) = 3.71 ± 0.00 for the reaction with Cl- and log(K1 Br/M-1) = 6.20 ± 0.05, log(K2 Br/M-1) = 4.55 ± 0.01 for the reaction with Br-. The two platinum atoms are nonequivalent in the HH dimer, in which the first deprotonation occurs selectively to the water molecule on the Pt(N4) atom and the first nucleophilic substitution with X- occurs preferentially to the Pt(N2O2) atom, where the atoms in parentheses are the coordinating atoms. The first water substitution with X- proceeds via two similar substitution paths, whereas the second substitution proceeds through two dissimilar paths: one is a simple substitution path and the other is via dissociation of the water molecule, providing a coordinatively unsaturated complex. These reaction paths are reasonably explained by the relative strength of the trans effect of the water, hydroxide, and halide ions in the monohalogeno complexes.

    AB - The following successive axial ligand substitution reactions of the head-to-head (HH) 2-pyridonato-bridged cis-diammineplatium(III) dinuclear complex ([(H2O)Pt(NH3)2(μ-C5H 4NO)2Pt(NH3)2(H2O)] 4+) with halide ions X- (X- = Cl- and Br-) to give monohalogeno and dihalogeno complexes were studied kinetically: [(H2O)Pt(NH3)2(μC5H 4NO)2Pt(NH3)2 (H2O)]4+ + X- ⇄ Kobs1 [(H2O)Pt(NH3)2(μ-C5H 4NO)2Pt(NH3)2(X)]3+ + H2O, [(H2O)Pt(NH3)2(μ-C5H 4NO)2Pt(NH3)2(X)]2 (X)]3+ + X- ⇄ Kobs2 [(X)Pt(NH3)2(μ-C5H4NO) 2Pt(NH3)2(X)]2+ +H2O. The acid dissociation constant (Kh1) of the axial aqua ligand in the HH dimer and the formation constants (K1 X and K2X of the monohalogeno and dihalogeno complexes were determined spectrophotometrically to be -log(Kh1/M) = 1.71 ± 0.04; log(K1 Cl/M-1) = 5.93 ± 0.02, log(K2 Cl/M-1) = 3.71 ± 0.00 for the reaction with Cl- and log(K1 Br/M-1) = 6.20 ± 0.05, log(K2 Br/M-1) = 4.55 ± 0.01 for the reaction with Br-. The two platinum atoms are nonequivalent in the HH dimer, in which the first deprotonation occurs selectively to the water molecule on the Pt(N4) atom and the first nucleophilic substitution with X- occurs preferentially to the Pt(N2O2) atom, where the atoms in parentheses are the coordinating atoms. The first water substitution with X- proceeds via two similar substitution paths, whereas the second substitution proceeds through two dissimilar paths: one is a simple substitution path and the other is via dissociation of the water molecule, providing a coordinatively unsaturated complex. These reaction paths are reasonably explained by the relative strength of the trans effect of the water, hydroxide, and halide ions in the monohalogeno complexes.

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