The Slowest Water Exchange at a Homoleptic Mononuclear Metal Center: Variable-Temperature and Variable-Pressure 17O NMR Study on [Ir(H2O)6]3+
| Autor: | Andre E. Merbach, David T. Richens, Urban Frey, Antonio Cusanelli |
|---|---|
| Rok vydání: | 1996 |
| Předmět: |
chemistry.chemical_classification
Analytical chemistry chemistry.chemical_element General Chemistry Kinetic energy Biochemistry Catalysis Metal chemistry.chemical_compound Colloid and Surface Chemistry Reaction rate constant chemistry visual_art visual_art.visual_art_medium Iridium Homoleptic Counterion Spectroscopy Trifluoromethanesulfonate |
| Zdroj: | Journal of the American Chemical Society. 118:5265-5271 |
| ISSN: | 1520-5126 0002-7863 |
| DOI: | 10.1021/ja954071n |
| Popis: | The rate constants and activation parameters for water exchange on hexaaqua and monohydroxy pentaaqua iridium(III) have been determined by 17O NMR spectroscopy as a function of temperature (358−406 K) and pressure (0.1−210 MPa) at several acidities (0.5−5.0 m). Noncoordinating trifluoromethanesulfonate (CF3SO3-) was used as the counterion. The observed rate constant was of the form k = k1 + k2/[H+], where the subscripts 1 and 2 refer to the exchange pathways on [Ir(H2O)6]3+ and [Ir(H2O)5(OH)]2+, respectively. The kinetic parameters obtained are summarized as follows: k1298 = (1.1 ± 0.1) × 10-10 s-1, ΔH1⧧ = 130.5 ± 0.6 kJ mol-1, ΔS1⧧ = +2.1 ± 1.7 J K-1 mol-1, and ΔV1⧧ = −5.7 ± 0.5 cm3 mol-1; k2298 = (1.4 ± 0.6) × 10-11 m s-1, ΔH2⧧ = 138.5 ± 4.5 kJ mol-1, ΔS2⧧ = +11.5 ± 11.6 J K-1 mol-1, and ΔV2⧧ = −0.2 ± 0.8 cm3 mol-1. The value obtained for k1298 corresponds to a residence time of ca. 300 years. The pKa298 and the volume change ΔVa0 associated with the first hydrolysis of [Ir(H2O)6]3+ were determined by ... |
| Databáze: | OpenAIRE |
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