Synthesis, spectroscopic characterisation of 1,1,2,3,4,5,6-heptahydro-1,1-di(carboxylato)telluranes and 1,3-dihydro-2λ 4-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-2λ 4-benzotellurole-2,2-diyl dibenzoate

Abstract

1,1,2,3,4,5,6-Heptahydro-1,1-di(carboxylato)telluranes C 5H 10Te(OCOR) 2 (R=OCO, C 6H 5, 4-NO 2C 6H 4, 3,5-(NO 2) 2C 6H 3, 4-OCH 3C 6H 4) and 1,3-dihydro-2λ 4-benzotellurole-2,2-diyl dicarboxylates C 8H 8Te(OCOR) 2 (R=CH 3, C 6H 5, 4-NO 2C 6H 4, 3,5-(NO 2) 2C 6H 3, 4-OCH 3C 6H 4, 4-NH 2C 6H 4) were obtained from the reactions of 1,1,2,3,4,5,6-heptahydro-1,1-diiodotellurane and 1,3-dihydro-2λ 4-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 (C 5H 10Te(OCOC 6H 5) 2 and C 8H 8Te(OCOC 6H 5) 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 C 5H 10 and C 8H 8 groups and the stereochemically active electron lone pair occupy equatorial positions. Te⋯O secondary bonds directed polymeric ( zig-zag chains) associations are present in C 5H 10Te(OCOC 6H 5) 2 (cf. trimeric associations in the precursor C 5H 10TeI 2) and tetrameric ( stair like) associations exist in C 8H 8Te(OCOC 6H 5) 2 (cf. polymeric associations in the precursor C 8H 8TeI 2).