Structural Trends in TeI2RR′: Crystal Structures and NMR Spectra of TeI2(CH2SiMe3)2, TeI2Th(CH2SiMe3), TeI2Ph(CH2SiMe3), and TeI2Th2 (Th=2-Thienyl, C4H3S)

TeI2(CH2SiMe3)(2) (1), TeI2Th(CH2SiMe3 (2), TeI2Ph(CH2SiMe3) (3), and TeI2Th2(4) (Th = 2-thienyl) were synthesized in excellent yields from the corresponding tellanes and I-2. The products were characterized by Te-125 NMR spectroscopy and single crystal X-ray crystallography. Each TeI2RR' molecule shows a trigonal bipyramidal coordination around tellurium with the iodine atoms occupying axial positions, and the organic groups and the lone pair occupying equatorial positions. The Te-I bonds and the I-Te-I angles in 1-4 span a range of 2.8407(9)-3.0194(10) angstrom and 171.85(2)-175.71(2)degrees, respectively. The Te-C bonds and C-Te-C angles show respective ranges of 2.100(6)-2.136(7) angstrom and 95.1(3)-100.9(3)degrees. In the solid state, the molecules show a varying degree of secondary bonding interactions. With the exception of TeI2(CH2SiMe3)(2)(1), the compounds show Te center dot center dot center dot I or I center dot center dot center dot I secondary bonding interactions leading to supramolecular assemblies. TeI2Ph(CH2SiMe3) crystallizes as two polymorphs. One (3a) is isomorphic with TeI2Th(CH2SiMe3) (2). The other (3b) shows a lattice of two alternating layers of molecules. In one layer, the molecules are linked into a two-dimensional network by Te center dot center dot center dot I and I center dot center dot center dot I interactions whereas the second layer consists of discrete dimers. The strongest Te center dot center dot center dot I secondary bonding interactions are observed for TeI2Th2. The lattice is composed of tetramers that is reminiscent of those in gamma- and delta-TeI4 and also have precedent in TeI2RR' species. The structures of TeI2Me2 and TeI2Ph2 have been considered for comparison. The trends in Te-125 NMR chemical shifts in TeI2RR'(R, R' = Me, CH2SiMe3, Th, Ph) are also discussed. (C) 2011 Wiley Periodicals, Inc. Heteroatom Chem 22:348-357, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/hc.20688