Solving the space group uncertainity of hexakis(dimethy1- sulfoxide)thallium(III) perchlorate using X-ray Crystallography and EXAFS techniques

The structure of the dimethyl sulfoxide solvated thallium(Il1) ion has been studied in dirnethylsulfoxide solution and in the solid state. X-ray crystallography shows a trigonal unit cell, space group R 3 (No. 148), for the [Tl(dmso)~](C104)3 compound with Z = 3, a - b == 1 1.9764(13) [11.8995(9)] A, c = 20.802(2) [20.467(2)] A; V - 2584.0(5) [2509.9(4)] A3, at 295 [150] K. The crystal structure shows a highly symmetric hexakis(dimethylsulfoxide)thallium(I1I) ion with thallium in a 3 symmetry site and a T1-0 bond distance of 2.224(3) A at 295 K. The octahedral T106 kernel is compressed along the three-fold axis with an 0-TI-0 bond angle of 96.20(1 1)'. The TI-0-S bond angle 120.7(2)', corresponds to a TI S distance of 3.292(2) A. One perchlorate ion centered on the 3 axis was described by a statistically disordered model. A low-temperature EXAFS study (10 K) resulted in the TI-0 and TI S distances 2.221(4) and 3.282(6) A, respectively, consistent with a TI-0-S bond angle of 120(1)'. The low Debye-Waller factors confirm a regular coordination without disorder of the dimethylsulfoxide ligands, which would have resulted from the alternative choice of space group, ~ 3for, th e crystal structure.