ORGANOTELLURIUM DI-IODIDES - MOLECULAR-STRUCTURE OF THE ALPHA-MODIFICATION OF 1,1-DIIODO-3,4-BENZO-1-TELLURACYCLOPENTANE, ALPHA-C8H8TEI2

The crystal and molecular structure of the thermochromic molecule, α-l,l-diiodo-3,4- benzo-1-teclluracyclopentane, α-C8H8TeI2 has been determined from three-dimensional X-ray data collected by counter techniques with monochromatized MoKα radiation. α-C8H8TeI2 is molecular. The configuration about tellurium is distorted octahedral with the two iodine atoms in axial positions. The benzylic carbon atoms and two iodine atoms from neighboring molecules occupy the equatorial positions. The intramoIecular Te-C (2.139(12), 2.145(12)») and Te-I (2.900(l). 2.928(l)») distances are normal. Two intermolecular Te⋯l interactions involving only one of the iodine atoms (l(2)) have distances of 3.6.53(l) and 3.878(l)». The shorter distance links the molecules into chains parallel to c̄ and the longer distance into chains along the 21 screw axis. The secondary bonding in yellow-orange α-C8H8TeI2 is relatively weak, and there are no short I⋯l distances. The compound is the lightest in color of the organo-tellurium iodides whose structures have been determined. The refinement, carried out using 1321 nonzero reflections for which 1≥3{digamma}(1), and assuming anisotropic thermal motion for all nonhydrogen atoms, led to a final value of the conventional R factor (on F) of 0.040. Crystal data (28°C) are as follows: space group P21 c,ā = 12.599(3), b̄ = 9.899(2), c̄ = 9.268(l)°, β = 104.89(l)° and V = 1117»3. The observed and calculated densities are 2.89(2)g/cm3 and 2.887(l)g/cm3, respectively. © 1979.