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Water-Exchange Mechanism of Tetraaquapalladium(II). A Variable-Pressure and Variable-Temperature Oxygen-17 NMR Study

✍ Scribed by Lothar Helm; Lars I. Elding; André E. Merbach

Publisher
John Wiley and Sons
Year
1984
Tongue
German
Weight
404 KB
Volume
67
Category
Article
ISSN
0018-019X

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✦ Synopsis

Water exchange of square-planar Pd(H,O):' 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 I70-FT-NMR line-widths of the resonance from coordinated water at 27.11 and 48.78 MHz. The following exchange parameters were obtained: k:&8 = (560 +C 40) s-', AH* = (49.5 f 1.9) kJ mol-I, AS* = -(26 f 6) J K-' mol-' and AV* = -(2.2 + 0.2) cm' mol-'. 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 rn, and are interpreted in terms of an associative (a) activation for the exchange. The exchange rate for Pd(H,O):+ is 1.4 x lo6 times faster than for Pt(H,O):+ at 298 K. A comparison with reactions between other nucleophiles and Pd(H,O):+ is also made.

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