Synthesis, spectroscopic characterisation of 1,1,2,3,4,5-hexahydro-1,1-dicarboxylatotellurophenes and crystal structures of 1,1,2,3,4,5-hexahydro-1,1-di(benzoato)- and 1,1-di(4-nitrobenzoato)tellurophene

1,1,2,3,4,5-hexahydro-1,1-dicarboxylatotellurophenes C4H8Te(OCOR)(2) (R = C H2Cl, C6H5, 4-NO2C6H4, 3,5-(NO2)(2)C6H3, 4-OCH3C6H4) were obtained from the reactions of 1,1,2,3,4,5-hexahydro-1,1-diiodotellurophene with silver oxid e and carboxylic acids or silver carboxylates. They were characterised by I R and (H-1,C-13, Te-125)-NMR spectroscopy. The structures of C4H8Te(OCOC6H5 )(2) and C4H8Te(4-NO2C6H4OCO)(2) were established by single-crystal X-ray d iffraction studies. In both cases the coordination geometry about the centr al Te atom can be described as pseudotrigonal bipyramidal in which two oxyg en atoms of the unidentate carboxylate groups are in the axial positions, t wo methylene carbon atoms (attached to Te) of the C4H8 group and the stereo chemically active electron lone pair occupy the equatorial positions. The m olecules are packed in their unit cells as the weakly bridged dimers throug h intermolecular Te ... O secondary bonds. (C) 1999 Elsevier Science S.A. A ll rights reserved.