Prakash C. Srivastava

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 ).

Secondary Bonding, C═H…O Hydrogen Bonding Assisted Supramolecular Associations and Charge Transfer (CT) Complexes of Organotelluriums and their Nonlinear Optical Properties

Abstract A library of supramolecular assemblies of acyclic- and cyclic organotelluriums assisted by intermolecular Te… X (X = Cl, Br, I, O, S) secondary bonds has been synthesized and X-ray characterized. In each case the immediate coordination geometry around the central Te atom is pseudotrigonal bipyramidal in which two methylene carbon atoms (attached to Te) in cyclic organotelluriums and methyl carbon atoms in acyclic organotelluriums and the stereochemically active electron lone pair occupy equatorial positions whereas the axial positions are occupied by halogen, oxygen or sulphur. They exists either as (a) ordered oligomers (trimeric, tetrameric, octameric aggregates) (b) cross linked chains, (c) zig-zag −2 dimensional ribbons and stairs, and (d) 3-dimensional supramolecular networks. It is observed that the supramolecular associations assisted by Te…O and Te…S secondary bonds are modified whereas those assisted by Te…halogen remain more or less the same vis-à-vis the supramolecular associations present in their precursors in the solid state. The first detection of C─H…O hydrogen bonds in organotellurium compounds has been done and their use in the synthesis of tellurium essential and ligand essential supramolecular assemblies is demonstrated. Tetraorganotelluroxanes obtained by easy and efficient routes represent the examples of cooperative participation of intermolecular and intramolecular Te…O secondary bonds and C─H…O hydrogen bonds. Hypervalent Te─I (formed through n → σ* orbital interactions) bonds in cyclic telluranes act as potential synthons for the formation of CT complexes possessing unusual structures. The utility of organotelluriums in the serendipitous synthesis of the first triphenyl methyl phosphonium salts of [C4H8TeI4]2− and [TeI6]2− anions is shown. The second harmonic generation (SHG) efficiency of some of these new supramolecular assemblies of organotelluriums indicates that the presence of C─H…O hydrogen bonds enhances their non linear optical (NLO) properties.

Synthesis, characterization and 1H NMR (experimental and theoretical) spectral studies of some neutral and anionic complexes of diphenyl tin isocyanate chloride

Abstract Neutral adducts and anionic complexes of Ph 2 Sn(NCO)Cl of the general formula Ph 2 Sn(NCO)Cl· n L ( n = 1, L = 2,2′-bipyridyl, ME 4 NCl; n = 2, L = DMSO and DMF) have been isolated. These complexes have been characterized through elemental analysis, molecular weight, molar conductance, IR and 1 H NMR data. Experimental 3 J [Sn 119 CCH(O)] ( 3 J exp. ) has been computed from the 1 H NMR spectra and it has been observed that there is an increase in 3 J exp. (Ph 2 Sn(NCO)Cl) on complexation. Further, 3 J [Sn 119 CCH(O)] has been calculated ( 3 J theor. ) and it is seen that there is close agreement between 3 J theor. and 3 J exp. values.

Organotellurium Derivatives—Synthesis, Structure, Supramolecular Associations and SHG Efficiency

Non‐covalent interactions [Te‐‐‐X (X=Cl, Br, I, O, S)], secondary bonds, and C‐H‐‐‐X (X=O, I) hydrogen bonds induced supramolecular associations of organotelluriums have been synthesised and X‐ray characterised. The immediate coordination geometry around a central tellurium atom is a pseudotrigonal bipyramidal with a stereochemically active electron lone pair. Tetraorganotelluroxanes, charge transfer (CT) complexes and bis (ferrocenyl carboxylato) telluranes, possibly useful in material science, have been synthesised and X‐ray characterised. Select organotellurium derivatives have been tested for their second harmonic generation (SHG) efficiency. Cyclic voltammetric studies of ferrocenyl carboxylato derivatives show that they may be useful for two‐electron redox catalysis.