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Australian Journal of Chemistry Australian Journal of Chemistry Society
An international journal for chemical science
RESEARCH ARTICLE

The exchange of dimethyl methylphosphonate on Pentakis(dimethyl methylphosphonate)dioxouranium(VI) ion

J Crea, SF Lincoln and EH Williams

Australian Journal of Chemistry 29(10) 2183 - 2188
Published: 1976

Abstract

The greatly predominant dioxouranium(V1) species existing in the presence of perchlorate anions in dilute dimethyl methylphosphonate (dmmp) solutions in CH2Cl2 diluent is shown from 1H N.M.R. studies to be [U02(dmmp)5]2+. Lineshape analyses of exchange-modified 1H N.M.R. lineshapes show the rate of dmmp exchange to be consistent with the rate law: kex5[U02(dmmp)52+] over a 9.7-fold variation of [dmmp]. A typical set of rate parameters is kex(268 K) = 82 ± 5 s-1, ΔH? = 57.3 ± 1.0 kJ mol-1 and ΔS? = 6.3 ± 3.6 J k-1 mol-1 for a solution in which [U02(dmmp)52+], [dmmp] and [CH2Cl2] are respectively 0.104, 0.515 and 13.59 mol dm-3. The mechanism of the exchange process, which is considered to be predominantly dissociative in nature, is discussed.

https://doi.org/10.1071/CH9762183

© CSIRO 1976

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