Structure of the Dimethyl Sulfoxide Solvated Thallium(III) Ion in Solution and in the Solid State Guibin Ma, †,‡ Alireza Molla-Abbassi, § Mikael Kritikos, § Andrey Ilyukhin, | Farideh Jalilehvand, ⊥ Vadim Kessler, O Mikhail Skripkin, §,# Magnus Sandstro 1 m,* ,§ Julius Glaser, † Jan Na 1 slund, O and Ingmar Persson* ,O Department of Chemistry, Royal Institute of Technology (KTH), SE-100 44 Stockholm, Sweden, Department of Structural Chemistry, Arrhenius Laboratory, University of Stockholm, SE-106 91 Stockholm, Sweden, Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Leninsky Prospect 31, Moscow 117907, Russia, Department of Chemistry, Stanford University, Stanford, California 94305-5080, and Department of Chemistry, Swedish University of Agricultural Sciences, SE-750 07 Uppsala, Sweden ReceiVed April 30, 2001 The structure and vibrational spectra of the dimethyl sulfoxide solvated thallium(III) ion have been studied in a dimethyl sulfoxide solution and in the solid state. X-ray crystallography shows a trigonal unit cell, space group R3 h (No. 148), for the [Tl(dmso) 6 ](ClO 4 ) 3 compound with Z ) 3, a ) b ) 11.9764(13) [11.8995(9)] Å, c ) 20.802(2) [20.467(2)] Å, and V ) 2584.0(5) [2509.9(4)] Å 3 at 295 [150] K. The crystal structure comprises a highly symmetric hexakis(dimethyl sulfoxide)thallium(III) ion, with thallium in a 3 h symmetry site and a Tl-O bond distance of 2.224(3) Å at 295 K. The octahedral TlO 6 kernel is compressed along the threefold axis with an O-Tl-O bond angle of 96.20(11)°. The Tl-O-S bond angle of 120.7(2)° corresponds to a Tl‚‚‚S distance of 3.292(2) Å. One perchlorate ion centered on the 3 h axis was described by a statistically disordered model. A low-temperature EXAFS study (10 K) resulted in the Tl-O and Tl‚‚‚S distances of 2.221(4) and 3.282(6) Å, respectively, consistent with a Tl-O-S bond angle of 120(1)°. The low Debye-Waller factors confirm a regular coordination without the disorder of the dimethyl sulfoxide ligands, which would have resulted from the alternative choice of space group R3 for the crystal structure. Raman and infrared spectra have been recorded and assigned, with the bands at 435 and 447 cm -1 corresponding to the vibrational frequency of the symmetric and asymmetric Tl-O stretching modes, respectively. EXAFS data of a 0.5 mol dm -3 thallium(III) trifluoromethanesulfonate in a dimethyl sulfoxide solution were consistent with that of a hexasolvated ion with mean Tl-O and Tl‚‚‚S distances of 2.22(1) and 3.33(2) Å, respectively, which correspond to a mean Tl-O-S bond angle of 124(2)°. The anomalously large disorder parameter for the Tl-O distances is consistent with a weak pseudo-Jahn-Teller effect. The 205 Tl, 13 C, and 1 H NMR spectra of the complex in solution show single signals at 1886, 39.5, and 2.3 ppm, respectively. Introduction Dimethyl sulfoxide is a polar aprotic solvent forming electrolyte solutions even with highly charged metal ions, thus allowing studies of their coordination and bonding properties. Stable solid dimethyl sulfoxide solvates can often be obtained and can be useful as sources of anhydrous metal ions in the syntheses of new compounds. Dimethyl sulfoxide is an ambi- dentate ligand, usually coordinating via the oxygen atom, but to a number of soft electron-pair acceptors, it is also coordinating via the sulfur atom. 1 An additional requirement for sulfur coordination seems to be a high availability of d electrons for metal-to-sulfur back-bonding, which is favored for the d 6 and d 8 transition-metal ions. 1 Thallium(III) can be classified as a medium-soft metal ion in contrast to the other trivalent ions of group 13, aluminum(III), gallium(III), and indium(III), which are regarded as hard from their coordination properties. 2 A characteristic property of thallium(III) is its high oxidizing power in the absence of strongly complex-forming ligands. The standard redox potential for the reduction to thallium(I) at 298 K in an acidic aqueous solution (with a unit activity of H + ) is e o (Tl 3+ /Tl + ) ) 1.25 V. 3 Even though thallium(III) is expected to strongly coordinate soft sulfur donor ligands, which is a stabilizing factor, it is spontaneously reduced to thallium(I) by the sulfur donor solvent N,N-dimethylthioformamide. 4 Thus, thallium(III) is only stable in a few solvents with a relatively high redox potential. We found the dimethyl sulfoxide solvated thallium(III) ion to be stable both in solution (by NMR studies) and in the solid state. Because the isoelectronic d 10 mercury(II) ion, which is softer * Corresponding author. † Royal Institute of Technology. ‡ Permanent address: Shanxi University, P. R. China. § University of Stockholm. | Russian Academy of Sciences. ⊥ Stanford University. O Swedish University of Agricultural Sciences. # Present address: St. Petersburg State University, St. Petersburg, Russia. (1) Calligaris, M.; Carugo, O. Coord. Chem. ReV. 1996, 153, 83. (2) To ´th, I.; Gyo ˜ri, B. Thallium: Inorganic Chemistry. In Encyclopedia of Inorganic Chemistry; King, R. B., Ed.; John Wiley and Sons: New York, 1994; Vol. 8, p 4134. (3) Handbook of Chemistry and Physics, 81st ed.; Lide, D. R., Ed.; CRC Press: Boca Raton, FL, 2000-2001; pp 8-28. (4) Persson, I.; Jalilehvand, F.; Sandstro ¨m, M. Inorg. Chem., in press. 6432 Inorg. Chem. 2001, 40, 6432-6438 10.1021/ic010453k CCC: $20.00 © 2001 American Chemical Society Published on Web 11/01/2001