Synthesis, spectroscopic characterisation of 1,1,2,3,4,5,6-heptahydro-1,1-di(carboxylato)telluranes and 1,3-dihydro-2λ4-benzotellurole-2,2-diyl dicarboxylates: Crystal structures of 1,1,2,3,4,5,6-heptahydro-1,1-di(benzoato)tellurane and 1,3-dihydro-2λ4-be

1,1,2,3,4,5,6-Heptahydro-1,1-di(carboxylato)telluranes C5H10Te(OCOR)2 (R=OCO, C6H5, 4-NO2C6H4, 3,5-(NO2)2C6H3, 4-OCH3C6H4) and 1,3-dihydro-2λ4-benzotellurole-2,2-diyl dicarboxylates C8H8Te(OCOR)2 (R=CH3, C6H5, 4-NO2C6H4, 3,5-(NO2)2C6H3, 4-OCH3C6H4, 4-NH2C6H4) were obtained from the reactions of 1,1,2,3,4,5,6-heptahydro-1,1-diiodotellurane and 1,3-dihydro-2λ4-benzotellurole-2,2-diyl diiodide with silver carboxylates. They were characterised by IR and (1H, 13C, 125Te)-NMR spectroscopy. UV, 13C/125Te CP/MAS spectra and thermogravimetric analysis of representative complexes are also described. The structures of (C5H10Te(OCOC6H5)2 and C8H8Te(OCOC6H5)2 were established by single crystal X-ray diffraction studies. In both cases the immediate coordination geometry about the central Te atom can be described as pseudo trigonal bipyramidal in which two oxygen atoms of the unidentate benzoate groups are in the axial positions, two methylene carbon atoms (attached to Te) of C5H10 and C8H8 groups and the stereochemically active electron lone pair occupy equatorial positions. Te⋯O secondary bonds directed polymeric (zig-zag chains) associations are present in C5H10Te(OCOC6H5)2 (cf. trimeric associations in the precursor C5H10TeI2) and tetrameric (stair like) associations exist in C8H8Te(OCOC6H5)2 (cf. polymeric associations in the precursor C8H8TeI2).