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Journal ArticleDOI

Synthesis of unusual mixed ligand tellurium(IV) dithiocarbamates with perchlorate. Crystal and molecular structure of perchloratotris(diethyldithiocarbamato)tellurium(IV)

01 Jan 1988-Polyhedron (Pergamon)-Vol. 7, Iss: 14, pp 1267-1271
Abstract: Synthetic and structural aspects of perchlorato complexes of tellurium(IV) with different dithiocarbamates (dtc) [(R1R2NCS2) where R1 = R2 = methyl, ethyl, n-propyl, i-propyl; R1R2 = (CH2)5(piperidine), C2H4OC2H4 (morpholine)] are reported. The crystal structure of TeL3ClO4 (where L = diethyl dtc) has been determined. The crystals of the complex are monoclinic, space group P21/n, a = 11.379(3), b = 17.745(7), c = 14.016(8) A, γ = 103.30(2)°, V = 2754.2 A3, F(000) = 1352, DX = 1.61 mg M−3. The final R and Rw values are 0.047 and 0.058, respectively for 5224 unique reflections. Tellurium displays a distorted dodecahedral stereochemistry formed by two interposing trapezoids, one resulting from the four sulphurs of two L groups and the other from the two sulphurs of the third L and the two oxygens of the perchlorate ion. The average TeS distance 2.648(2) A is close to that reported in other tris(dithiocarbamato)tellurium(IV) complexes. The perchlorate is weakly coordinated to tellurium(IV), with the average TeO distance being 2.994(8) A. The unusual coordination of perchlorate (as a bidentate ligand) to tellurium(IV) dithiocarbamate is reported for the first time.

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Topics: Perchlorate (57%), Dithiocarbamate (51%)
Citations
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Journal ArticleDOI
Abstract: A survey of the crystallographic literature of tellurium(II)/(IV) 1,1-dithiolates (dithiocarbamate, xanthate, dithiophosphate, or dithiophosphinate) is presented. Coordination numbers range from a low of three in some organotellurium(II) 1,1-dithiolates to a high of eight in the binary tellurium(IV) dithiocarbamates. The coordination geometries are rich and varied due to the stereochemical influence exerted by up to two lone pairs of electrons and the penchant of tellurium to increase its coordination number by forming secondary Te⋯X interactions, where X = sulphur, halide, tellurium, oxygen, and, in one case, a π system defined by a four-membered TeS2C chelate. Stereochemical roles of the lone pairs of electrons are always evident in the tellurium(II) structures. By contrast, a stereochemical position is not always evident for the lone pair of electrons in the tellurium(IV) derivatives, in particular in circumstances where the tellurium centre has a high coordination number. Supramolecular aggregation mediated by Te⋯X secondary interactions often leads to the formation of dimeric aggregates but sometimes to supramolecular polymers, and rarely three-dimensional networks. Comparisons between closely related structures clearly indicate that the dithiocarbamate ligand is a more effective chelating ligand compared with the other 1,1-dithiolate ligands covered in this survey. This difference in coordinating ability is clearly correlated with the observation that non-dithiocarbamate structures are more likely to form high-dimensional supramolecular architectures.

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38 citations


Journal ArticleDOI
Ajeet Singh1, J.K. Basumatary1Institutions (1)
Abstract: Ph 3 TeCl reacts with a molar equivalent of a sodium dithiocarbamate, xanthate, or dithiophosphate (S SNa) to give Ph 3 Te(S S) type derivatives. Molecular weight and conductivity measurements in solution suggest that these new triphenyltelluronium compounds are ionized in polar solvents but show a very strong tendency towards ion-association. The IR spectral data suggest that all these sulphur donors are coordinated in the η 1 mode in the new compounds. Their 1 H NMR spectra are characteristic, and are consistent with the monodentate behaviour of the S-ligands. Photolysis of their toluene/benzene/chloroform solutions (∼ 1 to 10 m M ) gives Ph 2 TeO, biphenyl, and disulphide. When O 2 is bubbled through their solutions during photolysis, TeO 2 is also formed. The rates of the UV-promoted decomposition decreases in the order xanthate > dithiocarbamate > dithiophosphate.

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15 citations


Journal ArticleDOI
01 Jan 1998-Polyhedron
Abstract: Two novel mixed-valent tellurium(II and IV) dithiocarbamate complexes have been prepared and their structures determined by X-ray diffraction studies. Complex 1, [TeIV(S2CNEt2)3]2[TeII(S2CNEt2)2](PF6)2, was obtained from the metathesis reaction of [TeIV(S2CNEt2)3ClO4] with KPF6 due to the partial reduction of the primary product [TeIV(SCNEt2)3]PF6, which is thermodynamically unstable. The preparation of tellurium(IV) dithiocarbamate in dilute perchloric acid medium results in complex 2, which has a composition [TeIV(S2CNEt2)3][TeII(S2CNEt2)2](ClO4). These two complexes represent the first examples of mixed valent complexes of tellurium consisting only the sulphur ligands. Their structural investigation shows that these complexes are stabilized primarily due to the supramolecular Te3.Te interaction, the distance of which is shorter than the earlier known complex. While TeII(S2CNEt2)2 is sandwiched between two TeIV(S2CNEt2)3 molecules in 1, two such Te(II) molecules are sandwiched in complex 2.

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2 citations


Journal ArticleDOI
R. Krishna Kumar1, G. Aravamudan1, M.R. Udupa1Institutions (1)
Abstract: Triphenylphosphine reduces tetrakis(diethyldithiocarbamato)tellurium(IV), TeL4 [L = diethyldithiocar-bamate, (C2H5)2NCS-2] to the tellurium(II) complex Tel2, on which PPh3 has no effect. The reaction of the tellurium(IV) complex, TeL2 (X = I, Br, Cl) with PPh3 in the molar ratio of 1:1 results in the formation of TeLX, CS2 and an aminophosphonium halide, (C2H5)2NP+Ph3X−. Another mole of PPh3 reduces TeLX further to elemental tellurium. The reactions of TeL3X (X = I, ClO4, PF6) systems with excess PPh3 lead interestingly to the formation of TeL2 and elemental tellurium, with the concomitant formation of CS2, (C2H5)2NP+Ph3 X − and (C2H5)2NC(S)P+Ph3X−. The reactions were performed in dichloromethane solutions and 31P NMR spectroscopy was widely used for the identification of various phosphorus containing species.

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1 citations


Journal ArticleDOI
Sp. Chidambaram1, G. Aravamudan1, M. Seshasayee1, T. A. Shibanova2  +1 moreInstitutions (2)
08 Nov 1988-ChemInform
Abstract: Synthetic and structural aspects of perchlorato complexes of tellurium(IV) with different dithiocarbamates (dtc) [(R1R2NCS2) where R1 = R2 = methyl, ethyl, n-propyl, i-propyl; R1R2 = (CH2)5(piperidine), C2H4OC2H4 (morpholine)] are reported. The crystal structure of TeL3ClO4 (where L = diethyl dtc) has been determined. The crystals of the complex are monoclinic, space group P21/n, a = 11.379(3), b = 17.745(7), c = 14.016(8) A, γ = 103.30(2)°, V = 2754.2 A3, F(000) = 1352, DX = 1.61 mg M−3. The final R and Rw values are 0.047 and 0.058, respectively for 5224 unique reflections. Tellurium displays a distorted dodecahedral stereochemistry formed by two interposing trapezoids, one resulting from the four sulphurs of two L groups and the other from the two sulphurs of the third L and the two oxygens of the perchlorate ion. The average TeS distance 2.648(2) A is close to that reported in other tris(dithiocarbamato)tellurium(IV) complexes. The perchlorate is weakly coordinated to tellurium(IV), with the average TeO distance being 2.994(8) A. The unusual coordination of perchlorate (as a bidentate ligand) to tellurium(IV) dithiocarbamate is reported for the first time.

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References
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Abstract: Anomalous scattering factors Δf′ and Δf″ have been calculated relativistically for Cr, Fe, Cu, Mo, and Ag Kα radiations for the atoms Li through Cf. An interpolation scheme for other wavelengths is included in a separate report. Relativistic calculations of the photoelectric cross section have been made and the integral for the principal contribution to Δf′ has been evaluated numerically without approximation to the form of the cross section‐vs‐energy curve, as has been done in previous calculations. Many of the results are significantly different from previous calculations. Where experimental values exist, agreement for Δf″ is improved. For the rare gases, except for xenon, agreement between Δf′ and experiment is improved. Because of the more rigorous evaluation of Δf′ from cross‐section information, it is presumed that the present Δf′ values are more accurate than previous calculated values. Calculated mass absorption coefficients for the elements are included as incidental information.

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Abstract: The x‐ray form factors for a bonded hydrogen in the hydrogen molecule have been calculated for a spherical approximation to the bonded atom. These factors may be better suited for the least‐squares refinement of x‐ray diffraction data from organic molecular crystals than those for the isolated hydrogen atom. It has been shown that within the spherical approximation for the bonded hydrogens in H2, a least‐squares refinement of the atomic positions will result in a bond length (Re value) short of neutron diffraction or spectroscopic values. The spherical atoms are optimally positioned 0.07 A off each proton into the bond. A nonspherical density for the bonded hydrogen atom in the hydrogen molecule has also been defined and the corresponding complex scattering factors have been calculated. The electronic density for the hydrogen molecule in these calculations was based on a modified form of the Kolos—Roothaan wavefunction for H2. Scattering calculations were made tractable by expansion of a plane wave in spheroidal wavefunctions.

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Journal ArticleDOI
Abstract: Le complexe est monomere a l'etat cristallin. La structure moleculaire presente une coordination bipyramidale pentagonale fortement deformee autour des atomes de tellure. Cristallisation dans le groupe P2 1 /n avec a=10,310, b=21,239 et c=13,331 A, β=103,34°, Z=4. Affinement jusqu'a R=0,035

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11 citations