A Coordination Chemistry Study of Solvated Thorium(IV) Ions in Two Oxygen-Donor Solvents

• The structures of the dimethyl sulfoxide (dmso) and N,N'-dimethylpropyleneurea (dmpu) solvated thorium(IV) ions have been studied in solution by extended X-ray absorption fine structure (EXAFS), and the structure of the solid oxonium bis[nonakis(O-dimethyl sulfoxide)]thorium(IV) trifluoromethanesulfonate dihydrate, (H3O)[Th((CH3)2SO)9]2(CF3SO3)9 center dot 2H2O (1) has been determined by single-crystal X-ray diffraction and EXAFS. Compound 1 was crystallized by evaporating a saturated dmso solution. It consists of two individual nonakis(O-dimethyl sulfoxide)thorium(IV) units, both of which have a tricapped trigonal prismatic configuration, as also found in nonakis(dimethyl sulfoxide)thorium(IV) perchlorate previously reported. Mean ThO bond lengths of 2.47 and 2.43 angstrom are found for the two structural units, respectively, for which the differences may be explained by differences in occupancy and temperature factors. The EXAFS data of 1 revealed mean ThO and SO bond lengths of 2.449(3) and 1.525(3) angstrom, respectively, and a ThOS bond angle of 135.2(5)inverted perpendicular to give a Th center dot center dot center dot S distance of 3.665(7) angstrom. In dmso solution, the mean ThO and SO bond lengths are 2.447(3) and 1.534(3) angstrom, respectively, the ThOS bond angle is 133.5(5)degrees, and there is a Th center dot center dot center dot C distance of 3.672(7) angstrom. The ThO bond-length distribution is somewhat asymmetric in both samples with Rmax values of 2.424 and 2.422 angstrom for 1 and solution, respectively. In dmpu solution, the ThO and CO bond lengths are 2.404(5) and 1.264(2) angstrom, respectively, and there is a ThOC angle of 157.1(5)degrees to give a Th center dot center dot center dot C distance of 3.594(7) angstrom. The observed ThO bond length indicates strongly that thorium(IV) is eight-coordinate in dmpu.

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NATURVETENSKAP  -- Kemi -- Oorganisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Inorganic Chemistry (hsv//eng)

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