The solvation of the dioxouranium(VI) ion by dimethyl sulfoxide

The species UO/sub 2/(DMSO)/sup 2 +//sub 5/ is shown from /sup 1/H NMR studies to be the predominant dioxouranium (VI) species existing in dilute anhydrous acetonedimethyl sulfoxide (DMSO) solutions, and this result is compared with data reported for the analogous water-acetone-dimethyl sulfoxide system. Complete line-shape analyses of exchange-modified /sup 1/H NMR line shapes indicate that the mechanism for DMSO exchange on UO/sub 2/(DMSO)/sup 2 +//sub 5/ is probably of the D or I/sub D/ type. A typical set of rate parameters are K/sub ex/(260/sup 0/K)/sub 0/ = 273 +- 14 sec/sup -1/, ..delta..H = 38.9 +- 0.5 kJ-mole/sup -1/, and ..delta..S = -47.5 +- 1.8 J-/sup 0/K/sup -1/-mole/sup -1/ for a solution in which (UO/sub 2/(DMSO)/sup 2 +//sub 5/), (DMSO), and (d/sub 6/ acetone) are, respectively, 0.0155, 0.0875, and 13.00 moles-dm/sup -3/.