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- Ducommun, Yves, et al.
(författare)
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1H NMR Kinetic Study of Dimethyl Sulfoxide Exchange on Tetrakis(dimethyl- sulfoxide)platinum(II) at Variable Temperature and Pressure : High-pressure NMR kinetics. 36.
- 1989
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 1520-510X .- 0020-1669. ; 28:2, s. 377-379
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Tidskriftsartikel (refereegranskat)abstract
- The present report is a 'H NMR investigation of the dimethyl sulfoxide exchange on Pt(Me2S0)42+ as a function of temperature and pressure in CD3N02. Dimethyl sulfoxide is an ambidentate ligand, and the complex contains two 0-bonded and two S-bonded ligands that are exchanging with the free ligand at different rates. It is favorable to follow these exchanges in a non-coordinating diluent like nitromethane, since it allows variation of the ligand concentration, thus giving an opportunity to establish the rate law. The use of a diluent of high dielectric constant and of uncharged ligands minimizes the electrostriction changes along the reaction path, so that the measured volumes of activation will reflect primarily the intrinsic changes of molecular volumes on going to the transition state.
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| 2. |
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| 3. |
- Ducommun, Yves, et al.
(författare)
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Variable Pressure Oxygen-17 FTNMR and Stopped-Flow Kinetic Study of Water Exchange and DMSO Substitution on Square-Planar Tetraaqua-Palladium(II) and -Platinum(II)
- 1984
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Ingår i: Journal de Physique. Colloques. - : EDP Sciences. - 0449-1947. ; 45:C8, s. 8-224
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Tidskriftsartikel (refereegranskat)abstract
- The very slow water exchange on Pt(H2O)42+ was studied in the temperature range 273 to 334 K and pressure range 0.1 to 228 MPa by 17O FTNMR, following the increase in height of the signal from bound water observed when platinum(II) solutions are mixed with 17O enriched water. The much faster water exchange on Pd(H2O)42+ was studied in the temperature range 240 to 345 K and pressure range 0.1 to 260 MPa, by measuring the 17O FTNMR line widths of the bound water resonance at 27.1 and 48.7 MHz. Complex formation between DMSO and Pd(H2O)42+ was studied by stopped-flow, in the temperature range 288 to 309 K and pressure range 0.1 to 175 MPa. In the three cases, the results are interpreted in terms of associative activation modes (a).
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| 4. |
- Frey, Urban, et al.
(författare)
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Proton NMR Kinetic Study of Ligand Exchange on Bis(1,4-dithiane)platinum(II), Bis(1,4-dithiane)palladium(II) and Tetrakis(dimethylsulfide)platinum(II) : High Presssure NMR Kinetics 51
- 1991
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 1520-510X .- 0020-1669. ; 30:26, s. 5033-5037
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Tidskriftsartikel (refereegranskat)abstract
- Ligand exchange on square-planar Pt(1,4-dithiane)2(2+), Pd(1,4-dithiane)2(2+), and Pt(Me2S)4(2+) has been studied as a function of temperature and pressure by H-1 NMR line-broadening, isotopic labeling, and magnetization transfer experiments with deuteriated nitromethane as solvent. Second-order rate constants and activation parameters are as follows: for 1,4-dithiane exchange on Pt(1,4-dithiane)2(2+), k2(298) = 28.8 +/- 4.8 m-1 s-1, DELTA-H double-ended dagger = 32.9 +/- 3.6 kJ mol-1, DELTA-S double-ended dagger = -106 +/- 11 J K-1 mol-1, and DELTA-V double-ended dagger = -12.6 +/- 1.1 cm3 mol-1; for 1,4-dithiane exchange on Pd(1,4-dithiane)2(2+), k2(298) = 9780 +/- 300 m-1 s-1, DELTA-H double-ended dagger = 22.9 +/- 0.6 kJ mol-1, DELTA-S double-ended dagger = -91.6 +/- 2.1 J K-1 mol-1, and DELTA-V double-ended dagger = -9.8 +/- 0.4 cm3 mol-1; for Me2S exchange on Pt(Me2S)4(2+), k2(298) = 1.54 +/- 0.07 m-1 s-1, DELTA-H double-ended dagger = 42.1 +/- 0.7 kJ mol-1, DELTA-S double-ended dagger = -100.2 +/- 2.2 J K-1 mol-1, and DELTA-V double-ended dagger = -22.0 +/- 1.3 cm3 mol-1. Second-order kinetics and negative entropies and volumes of activation indicate associative, I(a) or A, exchange mechanisms. For both metal centers, exchange of the chelated and strongly bound 1,4-dithiane, corrected for statistics, is faster than that of Me2S, probably due to steric factors. The ratio in reactivity for Pd/Pt is only ca. 1300 for Me2S and 340 for 1,4-dithiane, indicating a more pronounced sensitivity of Pt(II) to the electronic properties of the coordinated and entering ligands. Accordingly, activation volumes are more negative in the case of platinum. DELTA-V double-ended dagger for the Me2S exchange on Pt(II) is the most negative one reported so far for a square-planar solvent exchange.
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| 5. |
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| 6. |
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| 7. |
- Helm, Lothar, et al.
(författare)
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Water Exchange Mechanism of Tetraaquapalladium(II). A Variable Pressure and Variable Temperature Oxygen-217 NMR Study
- 1984
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Ingår i: Helvetica Chimica Acta. - : Wiley. - 0018-019X .- 1522-2675. ; 67:6, s. 1453-1460
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Tidskriftsartikel (refereegranskat)abstract
- Water exchange of square-planar Pd(H2O)42+ has been studied as a function of temperature (240 to 345 K) and pressure (0.1 to 260 MPa, at 324 K) by measuring the 17/O-FT-NMR line-widths of the resonance from coordinated water at 27.11 and 48.78 MHz. The following exchange parameters were obtained: k298ex = (560 ± 40) s−1, ΔH* = (49.5 ± 1.9) kJ mol−1, ΔS* = – (26 ± 6) J K−1 mol−1 and ΔV* = – (2.2 ± 0.2) cm3 mol−1. The values refer to an aqueous perchlorate medium with an ionic strength between 2.0 and 2.6 m and a perchloric acid concentration between 0.8 and 1.7 m, and are interpreted in terms of an associative (a) activation for the exchange. The exchange rate for Pd(H2O)42+ is 1.4 × 106 times faster than for Pt(H2O)42+ at 298 K. A comparison with reactions between other nucleophiles and Pd(H2O)42+ is also made.
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