Organotellurium Derivatives Research Articles

Carbonyl Activation by Selenium- and Tellurium-Based Chalcogen Bonding in a Michael Addition Reaction.

In the last years the use of chalcogen bonding—the noncovalent interaction involving electrophilic chalcogen centers—in noncovalent organocatalysis has received increased interest, particularly regarding the use of intermolecular Lewis acids. Herein, we present the first use of tellurium‐based catalysts for the activation of a carbonyl compound (and only the second such activation by chalcogen bonding in general). As benchmark reaction, the Michael‐type addition between trans‐crotonophenone and 1‐methylindole (and its derivatives) was investigated in the presence of various catalyst candidates. Whereas non‐chalcogen‐bonding reference compounds were inactive, strong rate accelerations of up to 1000 could be achieved by bidentate triazolium‐based chalcogen bond donors, with product yields of >90 % within 2 h of reaction time. Organotellurium derivatives were markedly more active than their selenium and sulphur analogues and non‐coordinating counterions like BArF 4 provide the strongest dicationic catalysts.

First evaluation of organotellurium derivatives as carbonic anhydrase I, II, IV, VII and IX inhibitors

A series of tellurides was evaluated as carbonic anhydrase (CA, EC 4.2.1.1) inhibitors against the human (h) carbonic anhydrase isoforms hCA I, II, IV, VII and IX, involved in a variety of diseases, including glaucoma, retinitis pigmentosa, epilepsy, arthritis and tumors. These compounds, which are the first tellurium-containing derivatives acting as inhibitors of carbonic anhydrase enzymes, showed effective inhibition against all isoforms investigated and some of them were selective for inhibiting the cytosolic or the membrane-bound CAs. Thus, these carbonic anhydrase inhibitors are interesting leads for the development of isoform-selective inhibitors.

Unraveling the Organotellurium Chemistry Applied to the Synthesis of Gold Nanomaterials.

Long-term preservation of the properties of gold nanoparticles in both solution and the dry powder form can be difficult. We have overcome this challenge by using organotellurium derivatives as both reducing agents and stabilizers in the synthesis of gold nanoparticles. This new synthetic protocol takes advantage of the photochemical and oxidative properties of diphenyl ditelluride (Ph2Te2), which, so far, have never been exploited in the synthesis of gold nanoparticles. The Au/Te core/shell (inorganic/organic) hybrid nanomaterial can be obtained in a one-step reaction, using only Ph2Te2 and HAuCl4. By modifying the reaction conditions, different resonance conditions of the gold core are achieved due to the formation of external shells with different thicknesses. The organotellurium shell can be easily removed by resuspension of the nanoparticles in environmentally friendly solvents, such as water or ethanol, making the Au core available for subsequent applications. A mechanism for the formation of core/shell nanoparticles has also been discussed.

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.

Intramolecularly Coordinated Organoselenium Darivatives: Syntheses, Structure and Reactivity

Although intramolecularly coordinated organotellurium derivatives have been extensively studied in recent years, the analogous derivatives of selenium have received little attention. We have recently started work on syntheses, structures and reactivity of intramolecularly coordinated organoselenium compounds. The synthesis of these compounds makes extensive use of the ortho-lithiation reaction followed by insertion of selenium into Li-C bond.

Hypervalent Tellurium Compounds Containing Te-N Interactions. Mononuclear and Polynuclear Derivatives

Various organotellurium derivatives containing the pendant arm (2-Me2NCH2)C6H4 group have been prepared and characterized. The structure of a hydrolysis by-product, [(Ph2TeCl)2O]2, was also established.

Intramolecular coordination in tellurium chemistry

Intramolecular coordination in organotellurium derivatives is reviewed. The various types of complexes are discussed according to the types of donor atoms involved. Structural and spectroscopic evidence in support of intramolecular coordination, where Te(II) and Te(IV) behave as Lewis acids, is emphasized.

ChemInform Abstract: The Action of Sodium Hydrogen Telluride on Olefins.

AbstractThe action of NaTeH on non‐electrophilic C=C bonds is investigated.

Synthesis and Characterisation of Diorganoselenium (IV) and Organotellurium (IV) Derivatives Containing Se-S or Te-S Bonds

Abstract Diorganoselenium (IV) derivatives containing Se-S bonds, diphenyl selenium (IV) bis-(O,O′-dialkyldithiophosphates) [Ph2Se{S2P(OR′)2}] [R′ = C2H5, CHMe2 and CH2CHMe2], diphenyl selenium (IV) bis-(O,O′-alkeylene dithiophos-phates) [Ph2Se(S2 POR″O)2] [R″ = -CH2C(Me)CH -, -CH(Me)CH2C(Me2) -] and organotellurium derivatives containing Te-S bonds, Organotellurium (IV) tris-(O,O′-dialkyl dithiophosphates) [Ph Te{S2P(OR′)2}3] [R′= CHMe2], Organotellurium (IV) tris-(O,O′ -alkylene dithiophosphates) [RTe(SPOR″O)3] [R = Ph or P -MeOC6H4 and R″ = -CH2CMe2CH2 -] have been prepared and characterised on the basis of physicochemical and spectral (IR, ″H and 31P NMR) studies. The results indicate a pseudo trigonal bipyramidal geometry around selenium atom where the four position are occupied by the two phenyl and two dithiophosphate ligands while remaining one vacant position is occupied by lone pair of electrons.

The action of sodium hydrogen telluride on olefins

The action of sodium hydrogen telluride, NaTeH, on non electrophilic carbon-arbon double bonds has been investigated.The reaction is found to be very sensitive to the substituents on the ethylenic linkage. Whereas phenyl conjugated olefins are reduced to alkylbenzenes,the reagent adds to isolated mono and disubstituted double bonds leading to organotellurium derivatives and with gem-disubstituted ones it leads to a mixture of reduction and addition products. These results are interpreted in terms of a radical pair mechanism involving hydrogen atom transfer from hydrogen telluride,HTe - to the double bond.

Synthesis and Antiviral Activity of Biphenylenetellurium-(IV) Dichloride and Its Reaction Products

Abstract Biphenylenetellurium(IV) dichloride has been prepared and its interactions with various silver salts Ag+X−, donor bases (L) and alkylammonium chloride R4NCl have been studied. Its reduction product biphenylene tellurium(II) undergoes oxidative addition with halogens and interhalogens. It also acts as a Lewis base forming molecular adducts with strong acceptors such as HgCl2. The newly synthesized compounds have been characterized through elemental analyses, molar conductance, IR and PMR spectroscopic data. A few organotellurium derivatives show appreciable antiviral activity.

Organotellurium derivatives—I. Cleavage of some metal-aryl bonds with tellurium tetrachloride

Organotellurium derivatives—I. Cleavage of some metal-aryl bonds with tellurium tetrachloride

Organotellurium derivatives : IV. Synthesis of some diaryltellurium dihalides and pseudohalides

Iodine monohalides (ICl, IBr), cyanogen halides (CNBr, CNI) and thiocyanogen (SCN) 2 add oxidatively to diaryltellurium(II), R 2Te (R  Ph, p-Ch 3OC 6H 4) under mild conditions (5̃°C). The resulting organotellurium(IV) derivatives react metathetically with silver pseudohalides to yield several new diaryltellurium(IV) pseudohalide derivatives.

Organotellurium derivatives of dicarboxylic acids

The freshly prepared sodium salts of ortho-phthalic acid and tetrabromo ortho-phthalic acid react with diaryltellurium dichlorides in chloroform to afford new dimeric organotellurium carboxylates, R 2Te(C 8X 4O 4) 2 (X = H, Br). The new compounds contain fourteen membered rings and the detailed structure is discussed particularly in the light of the 1H NMR spectrum of ( p-EtOC 6H 4) 2Te(C 8H 4O 4) 2 which shows inequivalence of p-ethoxy groups. The sebacate derivatives of tellurium(IV) are oligomeric and iso- and terephthalic acids failed to give well defined products.