Crystal and molecular structure of trans-tetrabromo- and trans-tetrachlorobis(tetramethylthiourea)tellurium(IV)

Abstract

Both trans-tetrabromo-and trans-tetrachlorobis(tetramethylthiourea)tellurium(IV), TeX4(CsH12NzS)2 (X = Br, Cl), are dark red substances forming orthorhombic crystals of space group symmetry Pbca and having four molecules per unit cell. Measured and calculated densities are 2.21 and 2.19 and 1.70 and 1.72 g for the bromide and chloride, rFspectively.The unit cell dimensions of the bromide are a = 14.98 f 0.03 A, b = 13.88 & 0.03 -4, and c = 10.40 =I= 0.02 A. For the chloride these are a = 14.74 j. 0.03 b, b = 13.87 f 0.03 d, and c = 10.06 f 0.02 A. Diffraction data for 861 and 596 independent, observed reflections for the bromide and chloride, repesctively, were collected using Cu KCL radiation and the multiple-film Weissenberg technique. Reflection intensities were estimated visually. In determining the structure of the bromide Patterson projections on h01 and hkO revealed the approximate positions of Te, Br, and S atoms. The positions of the C and N atoms were found by three-dimensional Fourier methods, and full-matrix, three-dimensional, least-squares refinement led to a final, conventional R value of 0.090. The refinement of the chloride proceeded, using trial atomic positions corresponding to those of the bromide structure, to an R value of 0.083. As required by tellurium's occupancy of a center of symmetry in the unit cell, the two sulfur atoms of each molecule are in trans positions. With the four halogen atoms they form a slightly distorted octahedral arrangement around the tellurium atom. The Te-S bond lengths of 2.707 f 0.01 and 2.699 f 0.008 A in the bromide and chloride, respectively, are significantly longer than the sum of the covalent radii, but the Te-Br distances of 2.707 f 0.007 and 2.686 =t 0.007 b and the Te-Cl distances of 2.536 j. 0.008 and 2.520 j. 0.008 b are in accord with the covalent radii sums.

Redox Reaction between Main‐Group Elements (Te, Sn, Bi) and N‐Heterocyclic‐Carbene‐Derived Selenium Halides: A Facile Method for the Preparation of Monomeric Halides

“…Even with this imposed symmetry there is a significant difference in two Se–Te–Cl bond angles, with Cl1–Te–Se [84.53(2)°] being significantly smaller than Cl1*–Te–Se [95.48(2)°]. The distorted‐octahedral geometry around the central tellurium has been reported for trans ‐tetrachlorobis(tetramethylthiourea)tellurium(IV), with S–Te–Cl bond angles ranging from 79 to 105°, and S1–Te–S2 is 174 to 180° 17,18,22. In compound 7d , all the Te–Cl bond lengths are equal, whereas in the related compounds the Te–Cl bond lengths are in the range of 2.455(1) to 2.601(1) Å 17,18,22.…”

“…The reaction, however, proceeded differently and afforded novel adducts of monomeric tellurium tetrahalides (i.e., TeX 4 ) coordinated with the resulting selones by means of a redox process. It is worth mentioning here that monomeric tellurium tetrahalides coordinated with thione,17 thiourea,18–20 and phosphene oxide21 are reported in the literature. These have been prepared from the reaction of tellurium tetrahalides (air‐ and moisture‐sensitive) with appropriate ligands.…”

The Nature of the Chemical Bond in Linear Three-Body Systems: From I3–to Mixed Chalcogen/Halogen and Trichalcogen Moieties

“… (a) References[142,169,173,180,181,184,188–190,203,206,217,219,233,240,360–362,368,373,374,376,381,473,480,481,565–699 (b) References [260, 325, 381, 469, 700–729]. (c) References [730–732].…”

“…(f) Reference [580]. (g) References [61, 183, 217, 220, 232, 233, 240, 318, 373, 411, 417, 480, 481, 558, 569, 574, 607, 615, 625, 627, 635, 651, 669, 675, 688, 691, 734–777]. …”

Reactions of 1,1-Diiodo-3,4-benzocyclopentatellurane with Sulfur and Selenium Ligands: X-Ray Structure of a Dicationic Telluraheterocycle, [C8H8Te{S=C(NMe2)2}2][BF4]2

“…Of particular interest has been evidence of the stereochemically active lone pair on tellurium (IV). 2 In contrast, some of the higher coordination numbers (six or above) also have a tellurium atom that displays no evidence for a stereochemical lone pair: Archetypal examples include TeX 6 2− [X = Cl, Br], 3,4 TeX 4 (tmtu) 2 [tmtu = tetramethylthiourea], 5 and TeL 4 compounds such as Te(dithiocarbamate) 4 . All of these examples show no intramolecular secondary bonding.…”