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Relevance of the Ligand Exchange Rate and Mechanism of fac-[(CO)3M(H2O)3]+ (M = Mn, Tc, Re) Complexes for New Radiopharmaceuticals.

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Title: Relevance of the Ligand Exchange Rate and Mechanism of fac-[(CO)3M(H2O)3]+ (M = Mn, Tc, Re) Complexes for New Radiopharmaceuticals.
Authors: Grundler, Pascal V.1, Helm, Lothar1 lothar.helm@epfl.ch, Alberto, Roger2 ariel@aci.unizh.ch, Merbach, André E.1
Source: Inorganic Chemistry. 12/11/2006, Vol. 45 Issue 25, p10378-10390. 13p. 3 Diagrams, 3 Charts, 5 Graphs.
Subjects: Ligands (Chemistry), Cobalt, Radiopharmaceuticals, Pyridazines, Carbonyl compounds, Inorganic chemistry, Inorganic compounds, Dimethyl sulfate
Abstract: The water exchange process on fac-[(CO)3Mn(H2O)3]+ and fac-[(CO)3Tc(H2O)3]+ was kinetically investigated by 17O NMR as a function of the acidity, temperature, and pressure. Up to pH 6.3 and 4.4, respectively, the exchange rate is not affected by the acidity, thus demonstrating that the contribution of the monohydroxo species fac-[(CO)3M-(OH)(H2O)2] is not significant, which correlates well with a higher pKa for these complexes compared to the homologue fac-[(CO)3Re(H2O)3]+ complex. The water exchange rate kex298/-1 (ΔHex‡/kJ mol-1; ΔSex‡/J mol-1 K-1; ΔV‡/cm³ mol-1) decreases down group 7 from Mn to Tc and Re: 23 (72.5; +24.4; +7.1) > 0.49 (78.3; +11.7; +3.8) > 5.4 × 10-3 (90.3; +14.5; -). For the Mn complex only, an O exchange on the carbonyl ligand could be measured (kCO338 = 4.3 × 10-6 s-1), which is several orders of magnitude slower than the water exchange. In the case of the Tc complex, the coupling between 17O (I = 5/2) and 99Tc (I = 9/2) nuclear spins has been observed (¹J99Tc, 17O = 80 ± 5 Hz). The substitution of water in fac-[(CO)3M(H2O)3]+ by dimethyl sulfide (DMS) is slightly faster than that by CH3CN: 3 times faster for Mn, 1.5 times faster for Tc, and 1.2 times faster for Re. The pressure dependence behavior is different for Mn and Re. For Mn, the change in volume to reach the transition state is always clearly positive (water exchange, CH3CN, DMS), indicating an Id mechanism. In the Case of Re, an Id/Ia changeover is assigned on the basis of reaction profiles with a strong volume maximum for pyrazine and a minimum for DMS as the entering ligand. [ABSTRACT FROM AUTHOR]
Copyright of Inorganic Chemistry is the property of American Chemical Society and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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  Data: Relevance of the Ligand Exchange Rate and Mechanism of fac-[(CO)<subscript>3</subscript>M(H<subscript>2</subscript>O)<subscript>3</subscript>]<superscript>+</superscript> (M = Mn, Tc, Re) Complexes for New Radiopharmaceuticals.
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  Data: <searchLink fieldCode="AR" term="%22Grundler%2C+Pascal+V%2E%22">Grundler, Pascal V.</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Helm%2C+Lothar%22">Helm, Lothar</searchLink><relatesTo>1</relatesTo><i> lothar.helm@epfl.ch</i><br /><searchLink fieldCode="AR" term="%22Alberto%2C+Roger%22">Alberto, Roger</searchLink><relatesTo>2</relatesTo><i> ariel@aci.unizh.ch</i><br /><searchLink fieldCode="AR" term="%22Merbach%2C+André+E%2E%22">Merbach, André E.</searchLink><relatesTo>1</relatesTo>
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  Data: <searchLink fieldCode="JN" term="%22Inorganic+Chemistry%22">Inorganic Chemistry</searchLink>. 12/11/2006, Vol. 45 Issue 25, p10378-10390. 13p. 3 Diagrams, 3 Charts, 5 Graphs.
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  Data: <searchLink fieldCode="DE" term="%22Ligands+%28Chemistry%29%22">Ligands (Chemistry)</searchLink><br /><searchLink fieldCode="DE" term="%22Cobalt%22">Cobalt</searchLink><br /><searchLink fieldCode="DE" term="%22Radiopharmaceuticals%22">Radiopharmaceuticals</searchLink><br /><searchLink fieldCode="DE" term="%22Pyridazines%22">Pyridazines</searchLink><br /><searchLink fieldCode="DE" term="%22Carbonyl+compounds%22">Carbonyl compounds</searchLink><br /><searchLink fieldCode="DE" term="%22Inorganic+chemistry%22">Inorganic chemistry</searchLink><br /><searchLink fieldCode="DE" term="%22Inorganic+compounds%22">Inorganic compounds</searchLink><br /><searchLink fieldCode="DE" term="%22Dimethyl+sulfate%22">Dimethyl sulfate</searchLink>
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  Data: The water exchange process on fac-[(CO)3Mn(H2O)3]+ and fac-[(CO)3Tc(H2O)3]+ was kinetically investigated by 17O NMR as a function of the acidity, temperature, and pressure. Up to pH 6.3 and 4.4, respectively, the exchange rate is not affected by the acidity, thus demonstrating that the contribution of the monohydroxo species fac-[(CO)3M-(OH)(H2O)2] is not significant, which correlates well with a higher pKa for these complexes compared to the homologue fac-[(CO)3Re(H2O)3]+ complex. The water exchange rate kex298/-1 (ΔHex‡/kJ mol-1; ΔSex‡/J mol-1 K-1; ΔV‡/cm³ mol-1) decreases down group 7 from Mn to Tc and Re: 23 (72.5; +24.4; +7.1) > 0.49 (78.3; +11.7; +3.8) > 5.4 × 10-3 (90.3; +14.5; -). For the Mn complex only, an O exchange on the carbonyl ligand could be measured (kCO338 = 4.3 × 10-6 s-1), which is several orders of magnitude slower than the water exchange. In the case of the Tc complex, the coupling between 17O (I = 5/2) and 99Tc (I = 9/2) nuclear spins has been observed (¹J99Tc, 17O = 80 ± 5 Hz). The substitution of water in fac-[(CO)3M(H2O)3]+ by dimethyl sulfide (DMS) is slightly faster than that by CH3CN: 3 times faster for Mn, 1.5 times faster for Tc, and 1.2 times faster for Re. The pressure dependence behavior is different for Mn and Re. For Mn, the change in volume to reach the transition state is always clearly positive (water exchange, CH3CN, DMS), indicating an Id mechanism. In the Case of Re, an Id/Ia changeover is assigned on the basis of reaction profiles with a strong volume maximum for pyrazine and a minimum for DMS as the entering ligand. [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>Copyright of Inorganic Chemistry is the property of American Chemical Society and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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RecordInfo BibRecord:
  BibEntity:
    Identifiers:
      – Type: doi
        Value: 10.1021/ic061578y
    Languages:
      – Code: eng
        Text: English
    PhysicalDescription:
      Pagination:
        PageCount: 13
        StartPage: 10378
    Subjects:
      – SubjectFull: Ligands (Chemistry)
        Type: general
      – SubjectFull: Cobalt
        Type: general
      – SubjectFull: Radiopharmaceuticals
        Type: general
      – SubjectFull: Pyridazines
        Type: general
      – SubjectFull: Carbonyl compounds
        Type: general
      – SubjectFull: Inorganic chemistry
        Type: general
      – SubjectFull: Inorganic compounds
        Type: general
      – SubjectFull: Dimethyl sulfate
        Type: general
    Titles:
      – TitleFull: Relevance of the Ligand Exchange Rate and Mechanism of fac-[(CO)3M(H2O)3]+ (M = Mn, Tc, Re) Complexes for New Radiopharmaceuticals.
        Type: main
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            NameFull: Grundler, Pascal V.
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            NameFull: Helm, Lothar
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            NameFull: Alberto, Roger
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            NameFull: Merbach, André E.
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            – D: 11
              M: 12
              Text: 12/11/2006
              Type: published
              Y: 2006
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              Value: 00201669
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              Value: 45
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              Value: 25
          Titles:
            – TitleFull: Inorganic Chemistry
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