The solid state conformation of diaryl ditellurides and diselenides: The crystal and molecular structures of (C4H3E)(2)E '(2) (E = O, S; E ' = Te, Se)

The crystal and molecular structures of dithienyl ditelluride (C4H3S)(2)Te- 2 (1), difuryl ditelluride (C4H3O)(2)Te-2 (2), dithienyl diselenide (C4H3S) (2)Se-2 (3), and difuryl diselenide (C4H3O)(2)Se-2 (4) are reported in this paper and compared to those of other simple diaryl ditellurides and disele nides. The chalcogen-chalcogen bonds exhibit approximately single bond leng ths [Te-Te = 2.7337(8) and 2.7240(4) Angstrom in 1 and 2, respectively; Se- Se = 2.357(1) and 2.368(2) Angstrom in 3 and 4, respectively], as do the ch alcogen-carbon bond lengths [Te-C = 2.095(9) - 2.104(6) in 1 and 2.091(6) - 2.105(9) Angstrom in 2; Se-C = 1.87(1) - 1.90(1) Angstrom in 3 and 1.887(8 ) - 1.897(10) Angstrom in 4]. The aromatic rings are disordered. The dihedr al angles C-E-E-C range from 79(2) to 96(1)degrees are consistent with the concept of minimized p lone-pair repulsion of adjacent chalcogen atoms. The dependence of molecular parameters on the angle between the aromatic rings and the chalcogen-chalcogen bonds follow trends established previously for aromatic disulfides. Though the bond parameters and conformations of 1 - 4 are similar, the packing of the molecules is different. The two ditellurid es 1 and 2 show short Te Te contacts (3.900 - 4.002 Angstrom in 1 and 4.060 - 4.172 Angstrom in 2). The two diselenides 3 and 4 do not exhibit close c halcogen-chalcogen interactions. The NMR spectroscopic properties of 1 - 4 are discussed.