The Crystal and Molecular Structures of (C

The Solid State Conformation of Diaryl Ditellurides and Diselenides:

The Crystal and Molecular Structures of (C

H

E)

E'

(E = O, S; E' = Te, Se) Raija Oilunkaniemi

, Risto S. Laitinen

, and Markku Ahlgr´en

aDepartment of Chemistry, P.O. Box 3000, FIN-90014 University of Oulu, Finland

bDepartment of Chemistry, University of Joensuu, P.O. Box 111, FIN-80101 Joensuu, Finland Reprint requests to Prof. R. S. Laitinen. Fax: +358-8-553-1608. E-mail: Risto.Laitinen@oulu.fi Z. Naturforsch.55 b,361–368 (2000); received January 21, 2000

Furyl Ditelluride, Thienyl Diselenide, Furyl Diselenide

The crystal and molecular structures of dithienyl ditelluride (C4H3S)2Te2 (1), difuryl ditelluride (C4H3O)2Te2 (2), dithienyl diselenide (C4H3S)2Se2 (3), and difuryl diselenide (C4H3O)2Se2(4) are reported in this paper and compared to those of other simple diaryl ditel- lurides and diselenides. The chalcogen-chalcogen bonds exhibit approximately single bond lengths [Te-Te = 2.7337(8) and 2.7240(4) ˚A in1and2, respectively; Se-Se = 2.357(1) and 2.368(2) ˚A in3and4, respectively], as do the chalcogen-carbon bond lengths [Te-C = 2.095(9) - 2.104(6) in1and 2.091(6) - 2.105(9) ˚A in2; Se-C = 1.87(1) - 1.90(1) ˚A in3and 1.887(8) - 1.897(10) ˚A in4]. The aromatic rings are disordered. The dihedral angles C-E-E-C range from 79(2) to 96(1)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 of1-4are similar, the packing of the molecules is different. The two ditellurides1and2show short TeTe contacts (3.900 - 4.002 ˚A in1and 4.060 - 4.172 ˚A in2). The two diselenides 3and4do not exhibit close chalcogen-chalcogen interactions. The NMR spectroscopic properties of1-4are discussed.