Cyclodimerization of phenyliodoacetylene with elemental tellurium: New pathway to 1.3-ditellurofulvenes

Thermal reaction between PhCCI and powdered Te afforded a mixture of (E)-4-iodo-2-(iodo(phenyl)-5-phenyl-1,3-ditellurofulvene (1) and (Z)-4-iodo-2-(iodo(phenyl)-5-phenyl-1-(diiodo),3-ditellurofulvene (2), which was subsequently reduced to (Z)-4-iodo-2-(iodo(phenyl)-5-phenyl-1,3-ditellurofulvene (3). Formation of 1 and 3 as the thermodynamically most stable products has been rationalized using density functional theory (DFT) calculations. Molecular structures of 1-3 were established crystallographically. In the solid state the coordination sphere of both tellurium atoms in 2 is extended by weak intermolecular Te?π interactions with the solvate molecule of toluene which completes the pseudo-trigonal bipyramidal coordination geometry around each Te atom and assembles 2 into the chains along the crystallographic c-axis.     

Regio- and stereo-specific addition of organotellurium trihalides to ferrocenylacetylene: Molecular and crystal structure of (Z)-halovinyl organotellurium dihalides

Organotellurium(IV) trihalides RTeX₃ (X = Br, I) reacts readily with ferrocenylacetylene to give (Z)-products of electrophilic addition to C-C triple bond: (Z)-FcXC = CTeX₂R (R = Ph, X = Br (1) or I (2); R = trans-8-ethoxy-4-cyclooctenyl, X = Br (3)). In case of PhTeX₃ (X = Br or I) the room temperature reaction is spontaneous and the structure of the product does not depends on the polarity of the solvent used; this is in contrast to the reaction of aryl-acetylenes with RTeBr₃ which were reported to afford (E)-bromovinyl aryltellurium dibromides in methanol and its (Z)-isomer in benzene. Molecular and crystal structures of new compounds and effect of bulky and electron-rich ferrocenyl substituent on the reactivity of acetylene moiety are discussed in this paper.     

Tellurium‐Halogen Secondary Bonding in the Crystal Structures of [Q]+[PhTeCl4]— (Q = C5NH6, 2‐Br‐C5NH5, {2‐Br‐C5NH5}{Co(NH3)4Cl2})

The reaction of diphenylditelluride with pyridine, 2‐bromopyridine or 2‐bromopyridine/tetraamminedichlorocobalt(III) chloride in 12 M hydrochloric acid afforded the tetrachlorophenyltellurate(IV) compounds [C₅NH₆][PhTeCl₄] ( 1 ), [2‐Br‐C₅NH₅] [PhTeCl₄] ( 2 ), and [{2‐Br‐C₅NH₅}{Co(NH₃)₄Cl₂}] [PhTeCl₄]₂ ( 3 ). They were all characterized structurally by single crystal X‐ray diffraction. In all structures, the arrangement about the tellurium atoms is square pyramidal. The [PhTeCl₄]^— anions in 1 and 2 form trimeric and dimeric units, respectively, through Te···Cl secondary bonding. Compound 3 shows an unusual face‐to‐face packing of the [PhTeCl₄]^—anions with hydrogen bonding to the bromopyridium cation.     

Supramolecular Assembling through Anionic Iodine Secondary Bonds: Synthesis and X‐ray Characterization of (Et4N)[PhTeI4] and (Et4N)[(β‐Naphthyl)TeI4]

[PhTe]₂ and [(β‐naphthyl)Te]₂ react with iodine and tetraethylammonium iodide in toluene/methanol to give (Et₄N)[PhTeI₄] and (Et₄N)[(β‐Naphthyl)TeI₄]. The complexes were analysed by single crystal X‐ray diffraction affording the centrosymmetric monoclinic space group P2₁/c. In the novel compounds only anionic interactions of the types Te···I and I···I take place, cation‐anion effective contacts do not occur. Both anions [PhTeI₄] and [(β‐naphthyl)TeI₄] exhibit square pyramidal coordination at tellurium, with the iodine atoms in the basal positions and the organic groups apical. The tellurium centers achieve an octahedral coordination in the whole lattices through Te···I secondary bonds with the adjacent ionic species. Only the Te–I‐ and I–I‐secondary bonds behave as structure‐forming interactions in the self‐organization of the supramolecular anionic gatherings. New evidences show that for organyltellurates (Q)[PhTeX₄] (Q = protonated amines, amides or amino acids; X = Cl, Br, I), NH···X hydrogen bondings are able to hinder the anionic halogen‐halogen secondary interactions. In case of the more frequent I···I interactions, they have been observed only in the absence of NH···I hydrogen bonds.     

Direct Michael addition to electron-deficient alkenes using diorganyl dichalcogenides (Te/S) and NaBH4/PEG-400

Nucleophilic species of tellurium and sulfur were generated in situ from the reaction of the respective diorganyl dichalcogenides with NaBH₄ in PEG-400 as solvent and selectively added to electron-deficient alkenes. Chalcogenolate anions were directly added at mild conditions by this simple procedure and in all cases furnished the respective Michael adducts in short reaction times and good yields.     

2,4,6-Triphenylphenyltellurium(IV) triiodide - supramolecular self-assembling in organotellurium triiodides

2,4,6-Triphenylphenyltellurium(IV) triiodide, (2,4,6-Ph₃C₆H₂)TeI₃, can be obtained by the reaction of the corresponding ditelluride {(2,4,6-Ph₃C₆H₂)Te}₂ with iodine under an atmosphere of dry nitrogen in toluene. The apparent bisphenoidal coordination sphere of the central tellurium atom is extended by the presence of intermolecular Te?I and I?I secondary bonds which form chains along the crystallographic a axis. Weak intramolecular interactions with one of the phenyl rings of the (2,4,6-Ph₃C₆H₅) unit completes the pseudo-octahedral coordination geometry around each tellurium atom. A comparison of the structure of (2,4,6-Ph₃C₆H₂)TeI₃ with the bonding situations in other organotellurium(IV) triiodides suggests a strong dependence of the formation of supramolecular assemblies on the nature of the organic substituents.     

Dimerization of New T‐shaped Hypervalent Organotellurium(II) Dihalides: Synthesis and Structural Characterization of (PyH)[mesTeIX] (Py = pyridine; mes = mesityl; X = Cl,Br, I)

[mesTe]₂ reacts with iodine in toluene and further with (C₅H₆N)⁺X^? (X = I, Br, Cl) to give (PyH)[mesTeI₂] ( 1 ), (PyH)[mesTeIBr] ( 2 ) and (PyH)[mesTeICl] ( 3 ). The anionic fragments [(mes)TeI₂] and [(mes)TeIBr] of 1 and 2 are assembled as dimers by reciprocal, secondary Te···X interactions, linked also to the pyridinium cations through μ‐NH···X bonding. The anion [(mes)TeICl]^? ( 3 ) do not interact with neighboring anionic moieties, achieving also secondary NH···Cl bonding toward the pyridinium cation. The dimerization ability – with attaining of additional interionic hydrogen bridges – of 1 and 2 allow them to be viewed as partially “molecular” and as hypervalent compounds of Te^II, for which the observed linearity of the I–Te–X system and the similarity of the Te–X bond distances are expected.     

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.