Formation mechanism of 2-methyl-2-buten-1,4-diol and 2-methyl-3-buten-1,2- diol from 2-methyl-1,3-butadiene on a head-to-head pivalamidato-bridged cis-diammineplatinum(III) binuclear complex

Jun Nagashima, Kazuhiro Shimazaki, Hideo Sekiya, Satoshi Iwatsuki, Koji Ishihara, Kazuko Matsumoto

    Research output: Contribution to journalArticle

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    Abstract

    Reactions of a pivalamidato-bridged head-to-head (HH) platinum(iii) binuclear complex with 2-methyl-1,3-butadiene (isoprene) and p-styrenesulfonate and of an α-pyrrolidonato-bridged HH platinum(iii) binuclear complex with p-styrenesulfonate were studied kinetically using UV-vis spectrophotometry and 1H NMR spectroscopy, and detailed reaction mechanisms are proposed. Pt(iii) binuclear complexes react with p-styrenesulfonate in four successive steps with mechanisms similar to that for an HH α-pyridonato-bridged Pt(iii) binuclear complex with p-styrenesulfonate. In the case of isoprene, four steps were observed on the basis of UV-vis spectrophotometry. However, the reaction kinetics for steps 1 and 2 correspond to those for the previous reaction system, and those for steps 3 and 4 do not correspond to those for the previous system or to those observed by using 1H NMR spectroscopy for the present isoprene system. By using UV-vis spectrophotometry, it was shown that isoprene preferentially π-coordinates to the Pt(N2O 2) atom via the double bond adjacent to the methyl group in step 1. In step 2, a second isoprene molecule π-coordinates to the Pt(N4) atom, which is the rate-determining step, followed by nucleophilic attack of a water molecule on the π-coordinated isoprene on the Pt(N2O 2) atom to form two isomeric σ-complexes. In the same step, π-coordinated isoprene on the Pt(N4) atom of the σ-complexes is released. This is different from the reaction of the Pt(iii) binuclear complexes with other olefins. In step 3, reductive elimination of the σ-complexes occurs to form two diols and the HH pivalamidato-bridged Pt(ii) binuclear complex. Finally, acid decomposition of the Pt(ii) binuclear complex occurs to form monomers in step 4. From 1H NMR spectroscopic observations, fast isomerization between σ-complexes and reductive elimination of the σ-complexes occurs in step 3, and isomerization from a 1,4-diol to a 1,2-diol occurs in step 4.

    Original languageEnglish
    Pages (from-to)6998-7007
    Number of pages10
    JournalDalton Transactions
    Volume40
    Issue number26
    DOIs
    Publication statusPublished - 2011 Jul 14

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    Spectrophotometry
    Atoms
    Isomerization
    Platinum
    Nuclear magnetic resonance spectroscopy
    Molecules
    isoprene
    Alkenes
    Reaction kinetics
    Monomers
    Nuclear magnetic resonance
    Decomposition
    Acids
    Water

    ASJC Scopus subject areas

    • Inorganic Chemistry

    Cite this

    Formation mechanism of 2-methyl-2-buten-1,4-diol and 2-methyl-3-buten-1,2- diol from 2-methyl-1,3-butadiene on a head-to-head pivalamidato-bridged cis-diammineplatinum(III) binuclear complex. / Nagashima, Jun; Shimazaki, Kazuhiro; Sekiya, Hideo; Iwatsuki, Satoshi; Ishihara, Koji; Matsumoto, Kazuko.

    In: Dalton Transactions, Vol. 40, No. 26, 14.07.2011, p. 6998-7007.

    Research output: Contribution to journalArticle

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    abstract = "Reactions of a pivalamidato-bridged head-to-head (HH) platinum(iii) binuclear complex with 2-methyl-1,3-butadiene (isoprene) and p-styrenesulfonate and of an α-pyrrolidonato-bridged HH platinum(iii) binuclear complex with p-styrenesulfonate were studied kinetically using UV-vis spectrophotometry and 1H NMR spectroscopy, and detailed reaction mechanisms are proposed. Pt(iii) binuclear complexes react with p-styrenesulfonate in four successive steps with mechanisms similar to that for an HH α-pyridonato-bridged Pt(iii) binuclear complex with p-styrenesulfonate. In the case of isoprene, four steps were observed on the basis of UV-vis spectrophotometry. However, the reaction kinetics for steps 1 and 2 correspond to those for the previous reaction system, and those for steps 3 and 4 do not correspond to those for the previous system or to those observed by using 1H NMR spectroscopy for the present isoprene system. By using UV-vis spectrophotometry, it was shown that isoprene preferentially π-coordinates to the Pt(N2O 2) atom via the double bond adjacent to the methyl group in step 1. In step 2, a second isoprene molecule π-coordinates to the Pt(N4) atom, which is the rate-determining step, followed by nucleophilic attack of a water molecule on the π-coordinated isoprene on the Pt(N2O 2) atom to form two isomeric σ-complexes. In the same step, π-coordinated isoprene on the Pt(N4) atom of the σ-complexes is released. This is different from the reaction of the Pt(iii) binuclear complexes with other olefins. In step 3, reductive elimination of the σ-complexes occurs to form two diols and the HH pivalamidato-bridged Pt(ii) binuclear complex. Finally, acid decomposition of the Pt(ii) binuclear complex occurs to form monomers in step 4. From 1H NMR spectroscopic observations, fast isomerization between σ-complexes and reductive elimination of the σ-complexes occurs in step 3, and isomerization from a 1,4-diol to a 1,2-diol occurs in step 4.",
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    T1 - Formation mechanism of 2-methyl-2-buten-1,4-diol and 2-methyl-3-buten-1,2- diol from 2-methyl-1,3-butadiene on a head-to-head pivalamidato-bridged cis-diammineplatinum(III) binuclear complex

    AU - Nagashima, Jun

    AU - Shimazaki, Kazuhiro

    AU - Sekiya, Hideo

    AU - Iwatsuki, Satoshi

    AU - Ishihara, Koji

    AU - Matsumoto, Kazuko

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    AB - Reactions of a pivalamidato-bridged head-to-head (HH) platinum(iii) binuclear complex with 2-methyl-1,3-butadiene (isoprene) and p-styrenesulfonate and of an α-pyrrolidonato-bridged HH platinum(iii) binuclear complex with p-styrenesulfonate were studied kinetically using UV-vis spectrophotometry and 1H NMR spectroscopy, and detailed reaction mechanisms are proposed. Pt(iii) binuclear complexes react with p-styrenesulfonate in four successive steps with mechanisms similar to that for an HH α-pyridonato-bridged Pt(iii) binuclear complex with p-styrenesulfonate. In the case of isoprene, four steps were observed on the basis of UV-vis spectrophotometry. However, the reaction kinetics for steps 1 and 2 correspond to those for the previous reaction system, and those for steps 3 and 4 do not correspond to those for the previous system or to those observed by using 1H NMR spectroscopy for the present isoprene system. By using UV-vis spectrophotometry, it was shown that isoprene preferentially π-coordinates to the Pt(N2O 2) atom via the double bond adjacent to the methyl group in step 1. In step 2, a second isoprene molecule π-coordinates to the Pt(N4) atom, which is the rate-determining step, followed by nucleophilic attack of a water molecule on the π-coordinated isoprene on the Pt(N2O 2) atom to form two isomeric σ-complexes. In the same step, π-coordinated isoprene on the Pt(N4) atom of the σ-complexes is released. This is different from the reaction of the Pt(iii) binuclear complexes with other olefins. In step 3, reductive elimination of the σ-complexes occurs to form two diols and the HH pivalamidato-bridged Pt(ii) binuclear complex. Finally, acid decomposition of the Pt(ii) binuclear complex occurs to form monomers in step 4. From 1H NMR spectroscopic observations, fast isomerization between σ-complexes and reductive elimination of the σ-complexes occurs in step 3, and isomerization from a 1,4-diol to a 1,2-diol occurs in step 4.

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