Synthese,Strukturen und Reaktivität von [(2,4,6-Ph3C6H2)Te(μ2-O)X]2 (X  Br und I)

Synthesis, Structures, and Reactivity of [(2,4,6-Ph₃C₆H₂)Te(μ₂-O)X]₂ (X ? Br, I) [(2,4,6-Ph₃C₆H₂)Te]₂ reacts with iodine affording the aryltellurenic halide (2,4,6-Ph₃C₆H₂)TeI, which is oxidized by oxygen to yield [(2,4,6-Ph₃C₆H₂)Te(μ₂-O)I]₂. It crystallizes with two molecules of dichloromethane in the monoclinic space group P2₁/c with a unit cell of the dimensions a = 911.3(4); b = 1153.3(2); c = 2244.1(9) pm; β = 93.53(2)°, Z = 2). The analogues bromo compound [(2,4,6-Ph₃C₆H₂)Te(μ₂-O)Br]₂ is obtained by the reaction of [(2,4,6-Ph₃C₆H₂)Te(μ₂-O)I]₂ with NH₄Br. It crystallizes with two molecules of xylene in the monoclinic space group P2₁/n (a = 1067.5(5); b = 1018.4(4); c = 2486.5(8) pm; β = 101.71(2)°; Z = 2). Both compounds are built up by two (2,4,6-Ph₃C₆H₂)TeX units (X ? Br, I) which are linked by two oxgen bridges to form centrosymmetric molecules. The Te? O? Te angles are 102°. Distinct Te? O bond lengths have been found (191.4(2) and 208.6(2) pm in [(2,4,6-Ph₃C₆H₂)Te(μ₂-O)I]₂ and 189.8(4)/208.4(5 pm in the bromo compound).     

Synthese und Struktur von [(Ph3C6H2)Te]2, [(Ph3C6H2)Te(AuPPh3)2]PF6 und [(Ph3C6H2)TeAuI2]2

Synthesis and Structure of [(Ph₃C₆H₂)Te]₂, [(Ph₃C₆H₂)Te(AuPPh₃)₂]PF₆ and [(Ph₃C₆H₂)TeAuI₂]₂ [(2,4,6-Ph₃C₆H₂)Te]₂ reacts with Ph₃PAu⁺ to yield [2,4,6-Ph₃C₆H₂TeAuPPh₃₂]PF₆ which can be oxidized by I₂ to form the gold(III) complex [(2,4,6-Ph₃C₆H₂)TeAuI₂]₂. [(2,4,6-Ph₃C₆H₂)Te]₂ crystallizes in the monoclinic space group P2₁/c with a = 810.6(2); b = 2026.5(5); c = 2260.6(7) pm; β = 99.23(3)° and Z = 4. In the crystal structure the ditelluride exhibits a dihedral angle C11? Te1? Te2? C21 of 66.1(2)°. The distance Te1? Te2 is 269.45(6) pm. In the cation of the triclinic complex [(2,4,6-Ph₃C₆H₂)Te(AuPPh₃)₂]PF₆ (space group P1 ; a = 1197.4(3); b = 1457.2(4); c = 1680.0(6) pm; α = 84.69(3)°; β = 85.11(3)°; γ = 75.54(3)°; Z = 2) a pyramidal skeleton RTeAu₂ with distances Te? Au = 259.2(1) and 257.8(2) pm and Au? Au = 295.3(1) pm is present. [(2,4,6-Ph₃C₆H₂)TeAuI₂]₂ crystallizes in the triclinic space group P1 with a = 1086.3(3); b = 1462.9(6); c = 1654.2(2) pm; α = 85.25(2)°; β = 87.44(1)°; γ = 80.90(3)°; Z = 2. In the centrosymmetrical dinuclear complex [(2,4,6-Ph₃C₆H₂)TeAuI₂]₂ the Au atoms exhibit a square-planar coordination by two iodine atoms and two tellurolate ligands. The tellurolate ligands form symmetrical bridges with distances Te? Au = 260.0 pm. The distances Au? I are in the range of 260.3(1) and 263.7(1) pm.     

Synthesis, spectral and structural characterisation of ditelluroxanes: μ-oxo-bis[nitrato-; 2,4,6-trinitrophenolato-dialkyl tellurium (IV)]

The synthesis of ditelluroxanes: μ-oxo-bis[nitrato dimethyl tellurium (IV)] [(CH₃)₂TeNO₃]₂O (1), μ-oxo-bis[(2,4,6-trinitro)phenolato dimethyl tellurium (IV)] [(CH₃)₂TeOC₆H₂(NO₂)₃]₂O (2) and μ-oxo-bis[1-(2,4,6-trinitro)phenolato-1,1,2,3,4,5-hexahydrotellurophene] [C₄H₈TeOC₆H₂(NO₂)₃]₂O (3) was achieved. 1 was synthesised by the reaction of (CH₃)₂TeI₂ with fuming HNO₃ while 2 and 3 were synthesised by the reactions of R₂Te(OH)₂ [R₂ = (CH₃)₂, (C₄H₈)] (in situ) with 2,4,6-trinitrophenol [ 2,4,6-(NO₂)₃C₆H₂OH] (picric acid). 1-3 have been investigated through UV/Vis; FT-IR, (¹H, ¹³C) NMR spectroscopy and single crystal X-ray diffraction studies. In 1-3 the immediate coordination geometry about the central tellurium atom can be described as pseudo trigonal bipyramidal and the stereochemically active electron lone pair occupying equatorial position. The supramolecular self-organisations of these tetraorgano ditelluroxanes (1-3) are explained through cooperative participation of Te?O secondary bonds, C-H?O hydrogen bonds and π-stacking of the organic substituents.     

Secondary bonding in functionalized organotellurium compounds: preparation and structural characterization of bis(acetamido)tellurium(IV) diiodide and bis(4-methylbenzoylmethyl)tellurium(II)

Elemental tellurium inserts, under mild conditions, between C-I bond of iodoacetamide to afford bis(acetamido)tellurium(IV) diiodide (NH₂COCH₂)₂TeI₂, 1. Heating of N-bromomethylphthalimide with activated tellurium powder however, resulted in the formation of bis(phthalimido)methane, 2, instead of the expected product bis(phthalimidomethyl)tellurium(IV) dibromide. The IR spectrum of 1 is indicative of intramolecular Te?OC interaction which is also substantiated by its single-crystal structure. The compound with planar small-bite chelating organic ligands acquires butterfly shape that imparts almost perfect C_2v molecular symmetry but unlike other organotellurium(IV) iodides, the solid state structure of 1 is devoid of any intermolecular Te?I or I?I secondary interactions owing to the presence of intramolecular Te?O secondary bonds as well as intermolecular N-H?O, N-H?I and C-H?I hydrogen bonds. Bis(4-methylbenzoylmethyl)telluride (4-MeC₆H₄COCH₂)₂Te, 3b, prepared by the reduction of the corresponding dibromide, is the first structurally characterized acyclic dialkyltelluride and interestingly, does not involve intramolecular Te?OC interaction invariably present in the parent dihalides (4-YC₆H₄COCH₂)₂TeX₂ (Y = H, X = I 4a; Y = H, X = Br 5a; Y = MeO, X = Br 5c). Weak intermolecular Te?Te and C-H?O hydrogen bonds appear to be the non covalent intermolecular associative forces that dominate its crystal packing in the solid state of this Te(II) derivative. The dialkyltellurides (4-YC₆H₄COCH₂)₂Te, (Y = H, 3a, Me, 3b) undergo oxidation in presence of (SCN)₂ to give the corresponding bis(isothiocyanato)tellurium(IV) derivatives and form 2:1 adducts with Pt(II) and Pd(II) chlorides.     

Structures of Iodophenyltellurium(II) and Diiododi-(β-naphtyl)tellurium(IV)

The reactions between diphenyl ditelluride, (PhTe)₂, or di(β-naphtyl)ditelluride, (β-naphtylTe)₂, with equivalent amounts of iodine have been reinvestigated and the crystal and molecular structures of iodophenyltellurium(II), (PhTeI)₄, and diiododi-(β-naphtyl)tellurium(IV), (β-naphtyl)₂TeI₂, have been determined. The structure of iodophenyltellurium(II) (space group Cc, a = 13.850(5) Å, b = 13.852(3) Å, c = 16.494(6) Å and β = 101.69(2)°, Z = 4) is built up by four PhTeI units which are linked by weak Te–Te interactions with Te–Te distances between 3.152(5) Å and 3.182(4) Å. The angles between the tellurium atoms are approximately 90° giving an almost perfect square. Long range secondary bonds (Te–I: about 4.2 Å) link the tetrameric units to give an infinite two-dimensional network. Iodo(β-naphtyl)tellurium(II) is less stable than the phenyl derivative. Solutions of this compound decompose under formation of elemental tellurium and (β-naphtyl)₂TeI₂. (β-Naphtyl)₂TeI₂ crystallises in the monoclinic space group C 2/c (a = 21.198(6) Å, b = 5.8921(8) Å, c = 16.651(5) Å, β = 114.77(2)°). The tellurium atom is situated on a two-fold crystallographic axis and Te–I and Te–C bond lengths of 2.899(1) and 2.108(7) Å have been determined.     

The crystal and molecular structure of acetato(2-phenylazophenyl-C,N′)tellurium(II) and (2-phenylazophenyl-C,N′)thiocyanatotellurium(II)

The crystal and molecular structures of acetato(2-phenylazophenyl-C,N′)tellurium(II) (I) and (2-phenylazophenyl-C,N′)thiocyanatotellurium(II) (II) have been determined. The structure of the former consists of discrete molecules in which weak intramolecular Te?ctdot;O [2.953(4) Å] interactions occur. However, the structure of the latter compound shows a very weak intermolecular Te?ctdot;N [3.535(3) Å] interaction, which links the molecules into dimers. The coordination about tellurium can be considered as approximately trigonal bipyramidal with the carbon atom and the two lone pairs in the equatorial positions and either N and O(I) or N and S (II) in the axial positions.     

New Mixed Ligand Organotellurium(IV) Compounds Containing Dithiocarbamates and the More Flexible Imidotetraphenyldithiodiphosphinates. The Crystal Structures of C8H8Te(S2CNEt2)[(SPPh2)2N] · H2O,C8H8Te(S2CNC5H10)[(SPPh2)2N], and C8H8Te(S2CNC4H8S)[(SPPh2)2N]

The synthesis of the following mixed ligand organotellurium(IV) compounds C₈H₈Te(S₂CNEt₂)[(SPPh₂)₂N] · H₂O ( 1 ), C₈H₈Te(S₂CNC₅H₁₀)[(SPPh₂)₂N] ( 2 ), C₈H₈Te(S₂CNC₄H₈O)[(SPPh₂)₂N] ( 3 ) and C₈H₈Te(S₂CNC₄H₈S)[(SPPh₂)₂N] ( 4 ) was achieved. They were characterized by IR, ¹H, ¹³C, ³¹P and ¹²⁵Te NMR, mass spectroscopy, and elemental analyses. The X‐ray crystal structures of 1 , 2 and 4 were determined. The both types of ligands display an asymmetrical chelating coordination mode on interaction with the tellurium atom. When these aniso‐bonded donor atoms are included in the coordination sphere, the tellurium atom exhibit an effective co‐ordination number of seven. The arrangement may be described as 1 : 2 : 2 : 2 coordination with a presumably stereoactive lone‐pair of electrons.     

Functionalized Organotellurium Halides: Synthesis,Characterization, and Observation of Intra- and Intermolecular Secondary Bonding

Abstract

Activated tellurium, but not selenium, reacts with para-substituted benzoylmethyl bromides as well as with iodoacetamide at their melting points in absence of a solvent to give bis(p-substituted benzoylmethyl)tellurium dibromides, (p-YC₆H₄COCH₂)₂TeBr₂, (Y = H, Me, and MeO) and bis(acetamido)tellurium diiodide, (H₂NCOCH₂)₂TeI₂, respectively. Quick reduction of (p-YC₆H₄COCH₂)₂TeBr₂, with sodium metabisulphite in a two-phase system yields crystalline (p-YC₆H₄COCH₂)₂Te. These tellurides undergo smooth oxidative addition of halogens, interhalogen ICl or a pseudohalogen (SCN)₂. Intramolecular coordination of the carbonyl group in these functionalized diorganotellurium dihalides is evident from IR spectra and shorter Te···O (carbonyl) distances in comparison to the sum of van der Waals radii and completes six coordination around Te atom. Not unexpectedly, therefore, intermolecular secondary bonding effects of the type Te…O, Te···X and X···X are missing in (PhCOCH₂)₂TeBr₂, (p-MeOC₆H₄COCH₂)TeBr₂ and (PhCOCH₂)₂TeI₂. Instead, these compounds provide rare examples, among organotellurium compounds, of supramolecular architecture, where C–H···Br and C–H···O hydrogen bonds and π-π (phenyl ring) interactions appear to be the noncovalent intermolecular associative forces that dominate the crystal packing.     

Tellurium(IV) Fluorides and Azides containing the Nitrogen Donor Substituent R = 2‐Me2NCH2C6H4; Crystal Structure of RTeF3 and of an Unusual Tellurium(VI) Fluoride Salt

The tellurenyl fluoride, 2‐Me₂NCH₂C₆H₄TeF, was obtained from reaction of the tellurenyl iodide RTeI with AgF. The compound was unambiguously identified by ¹⁹F and ¹²⁵Te NMR spectroscopy. The decomposition under disproportionation leads to the tellurium(IV) trifluoride, 2‐Me₂NCH₂C₆H₄TeF₃ and the ditelluride RTeTeR. The fluorination of the ditelluride, (2‐Me₂NCH₂C₆H₄Te)₂, with XeF₂ results in pure RTeF₃. The molecular structure of 2‐Me₂NCH₂C₆H₄TeF₃, the second structural characterized tellurium(IV) trifluoride, has been determined. Furthermore the syntheses of the new tellurium(IV) difluoride, (2‐Me₂NCH₂C₆H₄)₂TeF₂, and corresponding tellurium(IV) diazide, (2‐Me₂NCH₂C₆H₄)₂Te(N₃)₂ as well as the tellurium(IV) triazide, 2‐Me₂NCH₂C₆H₄Te(N₃)₃, and their characterization by spectroscopic methods were reported. During these investigations a rather interesting tellurium(VI) species was formed and the molecular structure of a subsequent product, [(2‐Me₂NHCH₂C₆H₄)₂TeF₃O]₂(SiF₆), was elucidated. Theoretical investigations for the compounds containing the stabilizing 2‐dimethylaminomethylphenyl substituent are illustrated.     

The structural diversity of Te-I interactions within tetraorganoditelluroxane diiodides and related compounds

Two tetraorganoditelluroxane diiodides (R₂Te)₂OI₂ (3, R = p-MeOC₆H₄; 5, R = Me) were prepared by the reaction of (p-MeOC₆H₄)₂TeI₂ (1) and (p-MeOC₆H₄)₂TeO (2) and the base hydrolysis of Me₂TeI₂ (4), respectively. The base hydrolysis of C₄H₈TeI₂ (8) afforded the tritelluroxane diiodide (C₄H₈Te)₃O₂I₂ (9). The reaction of Me₂TeI₂ (4) and Me₂Te(OH)₂ (6) in a ratio of 1:3 produced the coordination polymer of the composition 2 (Me₂Te)₂O(I)OH · H₂O (7). An attempt at preparing an adduct of 3 with iodine failed but provided co-crystals of (p-MeOC₆H₄)₂TeI₂ · I₂ (1a). The supramolecular structures of 1a, 3, 5, 7 and 9 are dominated by structurally directing secondary Te?I interactions.     

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.     

Twinning by merohedry in bis(4‐methoxyphenyl)tellurium(IV) diiodide dimethyl sulfoxide hemisolvate

Green crystals of the title compound, C₁₄H₁₄I₂O₂Te·0.5C₂H₆OS, space group P3₂, show twinning by merohedry (class II). The asymmetric unit contains two organotellurium molecules and one dimethyl sulfoxide (DMSO) molecule. The crystal structure displays secondary Te...I and Te...O(DMSO) bonds that lead to [(4‐MeOC₆H₄)₂TeI₂]₂·DMSO supramolecular units in which the two independent organotellurium molecules are bridged by the DMSO O atom. In addition to these secondary bonds, I...I interactions link translationally equivalent organotellurium molecules to form nearly linear ...I—Te—I...I—Te—I... chains. These chains are crosslinked, forming two‐dimensional arrays parallel to (001). The crystal packing consists of a stacking of these sheets, which are related by the 3₂ axis. This study describes an unusual dimeric arrangement of X—Te—X groups.     

Furan derivatives of tellurium: Synthesis and structural comparison with the thiophene analogues

α-Bromo-2-acetylfuran adds oxidatively to elemental tellurium and aryltellurium(II) bromide at ambient temperature to afford (2-furoylmethyl)tellurium(IV) dibromides, (FuCOCH₂)₂TeBr₂ (1b) and Ar(FuCOCH₂)TeBr₂ (Fu = 2-C₄H₃O; Ar = 1-C₁₀H₇, 2b; 2,4,6-Me₃C₆H₂, 3b). The iodo analogues 1c-3c can be obtained by metathesis of the bromides with an alkali iodide. Condensation reactions of the parent methyl ketone with Te(IV) chlorides results in the corresponding chloro analogues, (FuCOCH₂)₂TeCl₂ (1a) and Ar(FuCOCH₂)TeCl₂ (2a, 3a and Ar = 4-MeOC₆H₄ (4a)). These diorganotellurium dihalides are reduced with aqueous bisulfite to diorganotellurides 1-3, which can be oxidized readily with dihalogens to the desired diorganotellurium(IV) dihalides. The tellurated furan derivative, bis(2-furyl)tellurium(II), Fu₂Te (5), obtained by detelluration of bis(2-furyl)ditelluride with electrolytic copper, gives crystalline bis(2-furyl)tellurium(IV) dichloride (5a) upon chlorination. Crystal structures of Te(IV) compounds 1a, 1b, 2a-4a, and the telluride 3 together with its thiophene analogue (2,4,6-Me₃C₆H₂)((2-C₄H₃S)COCH₂)Te, 6 have been studied. Among the Te(IV) compounds, the functionalized organic moiety, FuCOCH₂-, behaves as a (C, O) chelating ligand, resulting in a intramolecular 1,4-Te?O secondary bonding interaction. Such an interaction is absent in Te(II) compounds 3 and 6, though they differ in the conformation adopted by the organic ligand. The chalcogen atoms in the heteroaroyl moiety are trans in 3 but cis in 6 which also possesses intermolecular Te?O interaction in its lattice.     

C(sp)H?O and C(sp)H?O hydrogen bonds in acyclic- and cyclic-organotellurium carboxylates

The reactions between R₂TeI₂ (R₂=(CH₃)₂, C₄H₈, C₅H₁₀) and AgOCOR′ (R′=C₆H₅, 4-NO₂C₆H₄, CHCHC₆H₅) (molar ratio 1:2) yield diorganotellurium dicarboxylates: (CH₃)₂Te(OCOC₆H₅)₂ (1), C₅H₁₀ Te(OCOC₆H₅)₂ (2), C₄H₈Te(OCO4-NO₂C₆H₄)₂ (3) and C₄H₈Te(OCOCHCHC₆H₅)₂ (4). They are characterized by IR, (¹H, ¹³C, ¹²⁵Te) solution NMR; (¹³C, ¹²⁵Te) 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.     

The crystal structures of 1-allyl-1-bromo-3,4-benzo-1-telluracyclopentane [C8H8Te(C3H5)Br], 1-phenacyl-1-bromo-3,4-benzo-1-telluracyclopentane [C8H8Te(C8H7O)Br] and 1-deuteromethyl-1-iodo-3,4-benzo-1-telluracyclopentane [C8H8Te(CD3)I]; the trans effect in organotellurium bromides and iodides

The crystal structures of the title compounds have been determined from three-dimensional X-ray counter data.C₈H₈Te(CH₂CHCH₂)Br (I) is orthorhombic, space group Pbca with a 9.642(1), b 25.586(7), c 9.680(3) Å, Z = 8. The structure has been refined to R 5.2% for 1262 observed reflections.C₈H₈Te(CH₂COPh)Br (II) is orthorhombic, space group Pccn with a 23.593(6), b 14.337(3), c 9.180(2) Å, Z = 8. R = 5.5% for 1374 reflections.C₈H₈Te(CD₃)I (III) is orthorhombic, space group Pbca with a 11.200(3), b 15.976(2), c 23.328(3) Å, Z = 16. R = 5.6% for 2142 reflections.In I and II, tellurium is coordinated in an approximately octahedral geometry by the organic residues and three halogen contacts, with TeC and TeBr distances in the ranges 2.14(1)–2.19(1) Å and 3.328(2)–3.368(2) Å in (I) and 2.12(1)–2.18(1) Å and 3.292(2)–3.391(2) Å in II.In III, each of the two crystallographically independent complexes has tellurium coordinated in a distorted octahedral geometry. The TeC bond lengths are 2.10(2)–2.16(2) Å. In each case two TeI distances are in the range 3.596(2)–3.688(2) Å and a third, longer interaction (3.870(2) and 4.112(2) Å) completes the coordination.In each of the structures I–III the three covalent TeC bonds are oriented cis within the octahedra and exert a trans bond-lengthening effect on the Tehalogen interactions, precluding covalent-type bonding; the structures are essentially ionic, (C₈H₈TeR)⁺ cations and halide anions forming extended arrays.     

Binuclear complexes of 4-methoxyphenyltellurium trichloride with variably linked diphosphine disulfide ligands

Four neutral ligands of the diphosphine disulfide type with different central linking groups [(CH₂)₄, (CH₂)₆, (C₆H₄)₂, and HN-(C₆H₄)-NH] were reacted with 4-methoxyphenyltellurium trichloride in dichloromethane. The crystallization of products afforded crystals consisting of binuclear addition complexes of 4-MeOC₆H₄TeCl₃ with corresponding ligands. The ligands are coordinated to Te(IV) centres through weak Te–S bonds. The coordination of both tellurium atoms in each complex is pseudo-octahedral, built of the TeCl₃S tetragonal basis and the aryl group and the lone pair of electrons in axial positions. The weak donating properties of sulfur atoms are reflected in shortening of the trans-positioned Te–Cl bonds.     

Benzyl­triethyl­ammonium 2,2,2,4‐tetra­chloro‐2,5‐di­hydro‐1,2λ5‐oxatellurole

The geometry around the Te atom in the anion in C₁₃H₂₂N⁺·C₃H₃Cl₄OTe^? is distorted pseudo‐octahedral with three Cl atoms and the O atom forming the equatorial plane, and the C atom lying opposite the tellurium lone pair. Distances and angles are: Te—O 2.0120 (18), Te—C 2.072 (2), Te—Cl 2.5239 (7), 2.5283 (7) and 2.5577 (7) Å; O—Te—C 81.61 (9), O—Te—Cl 90.69 (6), 90.99 (6) and 168.13 (5), C—Te—Cl 87.13 (8), 86.64 (8) and 86.59 (8), and Cl—Te—Cl 87.02 (2), 90.00 (3) and 173.24 (3)°. The anions are arranged in an infinite zigzag chain parallel to the a axis through a secondary Te?Cl bond [3.8391 (8) Å].     

X-ray characterization of Te(S2CNC5H10)2 and TeI2[(C13H10N2S)2] · 4C4H8TeI2; the first Te–C bond cleaved products obtained in the substitution reactions of organo(heterocyclic)tellurium(IV) derivatives

The reaction of organo(heterocyclic)tellurium(IV) derivative: C₈H₈TeI₂(1,3-dihydro-2λ⁴-benzotellurole-2,2-diyl diiodide) with NH₄S₂CNC₅H₁₀ (ammonium piperidine dithiocarbamate) gives C₈H₈Te(S₂CNC₅H₁₀)₂ (1) and Te(S₂CNC₅H₁₀)₂ (2) or C₈H₈TeI(S₂CNC₅H₁₀) (5) according to the reaction conditions. In such type of metathetical reactions, the formation of 2 is unprecedented and it corresponds to the first Te–C cleaved product. The reaction of 2 with CH₃I, yields the oxidative addition product, CH₃TeI(S₂CNC₅H₁₀)₂ (8). The formation of 2 is also supported through Quantum Chemical calculations. Another Te–C bond cleaved product TeI₂[(C₁₃H₁₀N₂S)₂] · 4C₄H₈TeI₂ (9) is obtained in the reaction of C₄H₈TeI₂ (1,1,2,3,4,5-hexahydro-1,1-diiodotellurophene) with NH₄S₂CNHC₆H₅ (ammonium aniline dithiocarbamate). The reaction of 1,1,2,3,4,5,6-heptahydro-1-iodo-1-(morpholine dithiocarbamato) tellurane [C₅H₁₀TeI(S₂CNC₄H₈O)] (10) with 1,10-phenanthroline gives an unusual product C₁₂H₈N₂ · C₄H₁₀INO (11). The structures of the new complexes 2, 8, 9, 10 and 11 have been determined by the X-ray analysis.     

Synthesis and molecular structure of niobocene trimethylacetate and its π-complex with diphenylacetylene

Niobocene trimethylacetate Cp₂Nb(OOCCMe₃) (I) does not react with usual n-donors (pyridine and triphenylphosphine), but readily adds a π-acceptor molecule of diphenylacetylene (tolane) in benzene to form Cp₂Nb(OOCCMe₃)(π-Ph₂C₂) · 0.5 C₆H₆ (II). The structures of the diamagnetic complexes I and II have been determined by an X-ray diffraction study. These molecules represent wedge-like sandwiches wit dihedral angles between cyclopentadienyl ligands equal to 44.4 and 50.7°, and average NbC distances of 2.39 and 2.44 Å, respectively. The bisector plane of I contains the chelate trimethylacetate group (NbO bond lenghts 2.23 and 2.24 Å) and that of II contains the coordinated tolane molecule and the oxygen atom of the terminal trimethylacetate ligand (NbO 2.16, NbC 2.18 and 2.19, CC 1.29 Å, PhCC angles 141 and 146°). An unusually large splitting of OCO stretching frequencies is observed in the IR spectrum of I (1652?1305 = 347 cm^?1). Structural characteristics of the coordinated CC triple bond in II are similar to those found in Cp(π-Ph₄C₄)Nb(CO)(π-Ph₂C₂) studied earlier. The role played by the Nb^III lone pair in I and II is discussed.     

Synthesis and polycondensation of some new organotellurium compounds containing hydroxymethyl groups

A new series of organotellurium compounds [i.e. 2‐HOCH₂C₆H₄TeBr₃ (1), (2‐HOCH₂C₆H₄)₂TeBr₂ (2), (2‐HOCH₂C₆H₄)₂Te (3), (2‐HOCH₂C₆H₄Te? )₂ (4), 4‐HOCH₂C₆H₄TeBr₃ (5), (4‐HOCH₂C₆H₄)₂TeBr₂ (6), (4‐HOCH₂C₆H₄)₂Te (7), and (4‐HOCH₂C₆H₄Te? )₂ (8)] were prepared by reacting hydroxymethylphenylmercury chlorides with tellurium tetrabromide in dry dioxane. Bis(2‐hydroxymethylphenyl) telluride (3), bis(2‐hydroxymethylphenyl) ditelluride (4) and bis(4‐hydroxymethylphenyl) telluride (7) were polymerized by a solution polycondensation technique with toluene diisocyanate and terephthaloyl chloride, leading to new organic tellurium polyurethanes and polyesters. All the new compounds were characterized by elemental analysis and spectroscopic data. Copyright © 2002 John Wiley & Sons, Ltd.