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- Helm, Lothar, et al.
(author)
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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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In: Helvetica Chimica Acta. - : Wiley. - 0018-019X .- 1522-2675. ; 67:6, s. 1453-1460
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Journal article (peer-reviewed)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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