Sangeeta Bajpai

DIMETHYL TELLURIUM(IV) DERIVATIVES : SYNTHESIS, SPECTROSCOPIC CHARACTERISATION AND STRUCTURES OF ME2TEBR2 AND ME2TE(OCOC6H5)2

The comparative solution 1H-NMR spectra and solid state crystal structures of dimethyltellurium dihalides, Me2TeX2 (X=CI, Br, I) are described. The dimethyltellurium dicarboxylates, Me2TeX′2 (X′=OCOC6H5, OCOCH3, OCO) were obtained from the reactions of Me2TeI2 with silver carboxylates. They were characterised by IR, 1H- and 13C-NMR spectroscopy. The structures of Me2TeBr2 and Me2Te(OCOC6H5)2 were established by single crystal X-ray diffraction studies. Both possess immediate distorted trigonal bipyramidal geometries with a stereochemically active electron lone pair and the latter contains weak intermolecular C–H⋯O interactions.

Secondary bonds induced supramolecular assemblies in the crystals of 1,1,2,3,4,5-hexahydro-1,1-diiodotellurophene; 1,1,2,3,4,5,6-heptahydro-1,1-diiodotellurane and 1,3-dihydro-2λ4-benzotellurole-2,2-diyl diiodide

Abstract The comparative study of crystal structures of heterocyclic organotellurium diiodides viz. 1,1,2,3,4,5-hexahydro-1,1-diiodotellurophene (C4H8TeI2) (1); 1,1,2,3,4,5,6-heptahydro-1,1-diiodotellurane (C5H10TeI2) (2), and 1,3-dihydro-2λ4-benzotellurole-2,2-diyl diiodide (C8H8TeI2) (3), with respect to polymorphism, bond lengths, bond angles; (a) TeI; (b) TeC; (c) ITeI; (d) CTeC; (e) CTeI, and intermolecular secondary bonds; (f) Te⋯I; (g) ITe⋯I; and (h) CTe⋯I, are described. The structures of all heterocyclic organotellurium diiodides were established by single crystal X-ray diffraction studies. In each case a distorted octahedral (six-coordinate) geometry exists around tellurium atom with Te⋯I secondary bonds leading to 2-dimensional zigzag ribbons in 1, trimeric molecular aggregates in 2 while 3 is a 3-dimensional polymer.

C(sp3)-H...O and C(sp2)-H...O hydrogen bonds in acyclic- and cyclic-organotellurium carboxylates

Abstract The reactions between R 2 TeI 2 (R 2 =(CH 3 ) 2 , C 4 H 8 , C 5 H 10 ) and AgOCOR′ (R′=C 6 H 5 , 4-NO 2 C 6 H 4 , CHCHC 6 H 5 ) (molar ratio 1:2) yield diorganotellurium dicarboxylates: (CH 3 ) 2 Te(OCOC 6 H 5 ) 2 ( 1 ), C 5 H 10 Te(OCOC 6 H 5 ) 2 ( 2 ), C 4 H 8 Te(OCO4-NO 2 C 6 H 4 ) 2 ( 3 ) and C 4 H 8 Te(OCOCHCHC 6 H 5 ) 2 ( 4 ). They are characterized by IR, ( 1 H, 13 C, 125 Te) solution NMR; ( 13 C, 125 Te) solid state NMR spectroscopy. The X-ray structures of 1 – 4 (the immediate environment about tellurium is that of distorted trigonal bipyramidal geometry with a stereochemically active electron lone pair) are described in the context of their ability to generate intermolecular CH⋯O hydrogen bonds, which lead to the formation of supramolecular assemblies.

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

Abstract 1,1,2,3,4,5-hexahydro-1,1-dicarboxylatotellurophenes C4H8Te(OCOR)2 (R=CH2Cl, C6H5, 4-NO2C6H4, 3,5-(NO2)2C6H3, 4-OCH3C6H4) were obtained from the reactions of 1,1,2,3,4,5-hexahydro-1,1-diiodotellurophene with silver oxide and carboxylic acids or silver carboxylates. They were characterised by IR and (1H, 13C, 125Te)-NMR spectroscopy. The structures of C4H8Te(OCOC6H5)2 and C4H8Te(4-NO2C6H4OCO)2 were established by single-crystal X-ray diffraction studies. In both cases the coordination geometry about the central Te atom can be described as pseudotrigonal bipyramidal in which two oxygen atoms of the unidentate carboxylate groups are in the axial positions, two methylene carbon atoms (attached to Te) of the C4H8 group and the stereochemically active electron lone pair occupy the equatorial positions. The molecules are packed in their unit cells as the weakly bridged dimers through intermolecular Te⋯O secondary bonds.

A UNIQUE SUPRAMOLECULAR STRUCTURE OF POLY [μ-OXO -BIS(1,1,2,3,4,5-HEXAHYDRO-1-NITRATOTELLUROPHENE)] [(C4H8TENO3)2O]N WITH—0-TE-0-TE-0—CROSS LINKED CHAINS

Abstract Poly [μ-oxo bis(1,1,2,3,4.5-hexahydro- 1-nitratotellurophene)] 1, is prepared by the room temperature reaction of 1,1,2,3,4,5-hexahydro- 1.1 -diiodotellurophene with silver nitrate in deionised water. Crystals of 1 are monoclinic. space group CUc with a=13.930(2) Å, b =11.665(2) Å, c=10.0682(11) Å, β=116.264(8)O and Z=A. The monomeric unit of the title compound is centrosymmetric, with an angular TeOTe skeleton containing bridging O atom at the centre of symmetry. These monomeric units are linked together through —O-Te-O-Te-O—cross linked chains and the nitrate groups are asymmetrically bidentate with a primary Te-ONO2 and a secondary Te—O semibonding interaction. Each nitrate group further participates in another Te–O semibonding interaction forming another asymmetric Te(NO3)2Te bridge. The structural characteristics of 1 are compared with related complexes.

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-benzotellurole-2,2-diyl dibenzoate

1,1,2,3,4,5,6-Heptahydro-1,1-di(carboxylato)telluranes C 5 H 1 0 Te(OCOR) 2 (R=OCO, C 6 H 5 , 4-NO 2 C 6 H 4 , 3,5-(NO 2 ) 2 C 6 H 3 , 4-OCH 3 C 6 H 4 ) and 1,3-dihydro-2λ 4 -benzotellurole-2,2-diyl dicarboxylates C 8 H 8 Te(OCOR) 2 (R=CH 3 , C 6 H 5 , 4-NO 2 C 6 H 4 , 3,5-(NO 2 ) 2 C 6 H 3 , 4-OCH 3 C 6 H 4 , 4-NH 2 C 6 H 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 ( 1 H, 1 3 C, 1 2 5 Te)-NMR spectroscopy. UV, 1 3 C/ 1 2 5 Te CP/MAS spectra and thermogravimetric analysis of representative complexes are also described. The structures of (C 5 H 1 0 Te(OCOC 6 H 5 ) 2 and C 8 H 8 Te(OCOC 6 H 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 5 H 1 0 and C 8 H 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 5 H 1 0 Te(OCOC 6 H 5 ) 2 (cf. trimeric associations in the precursor C 5 H 1 0 TeI 2 ) and tetrameric (stair like) associations exist in C 8 H 8 Te(OCOC 6 H 5 ) 2 (cf. polymeric associations in the precursor C 8 H 8 TeI 2 ).