I. D. Sadekov

Molecular and crystal structure of ortho-tellurated azomethines with intramolecular N → Te coordination

Abstract Novel reactions have been discovered and studied of C aliph. –Te bond scission in o -butyltellurobenzalanilines under the action of halogens, which afford 2-halogenotellurenyl- and 2-trihalogenotellurobenzalanilnes in high yields. The series of azomethines have been synthesized with different tellurium-containing groups in o -positions with respect to the CN bond. The effects of structural factors upon the length of N → Te intramolecular coordination bonds have been studied by the following methods: X-ray structural determinations, dipole moments, 1 H and 125 Te NMR spectroscopy and IR spectroscopy. In Te II derivatives, the shortest intramolecular N→ Te contact (2.23 A) is formed in 2-chlorotellurenyl derivatives XIIIb. Bis(2-formylphenyl)tellurium imines XIVa exist in the crystal form as 10-Te-3 telluranes, in which long intramolecular fractional N → Te bonds (2.70–2.72 A) have been detected, with the basicity of the imine N atom no practical effect on their length. The 125 Te NMR spectrum of the 15 N labelled bis[2-(phenyl)iminomethinylphenyl]telluride shows that in solution of this compound a very fast (on an NMR timescale), Te–N and Te ← N bond scrambling occurs owing to a dynamic equilibrium between the topomeric 10-Te-3 structures that apparently takes place via the 12-Te-4 tellurane intermediates. The intramolecular coordination bond in the Te iv derivative, (2-phenyliminomethinyl-phenyl)butylmethyl telluronium perchlorate, belongs to the longest Te → N bonds (2.75 A). For the first time, the 125 Te– 15 N spin-spin coupling constants are reported for a number of o -tellurated azomethines.

Chemical consequences of intramolecular Te ← N coordination in tellurium-containing aromatic azomethine derivatives

Abstract Owing to stabilization by Te ← N coordination in the aromatic tellurenyl compounds containing the azomethine function in the ortho position of the aryl ring, the synthesis of the novel organic tellurium compounds, tellurenyl azides and tellurenic acid esters and anhydrides becomes possible. The influence of the Te ← N coordination on the reactions of 2-butyltelluro- and 2-halogenotellurenylbenzalanilines is described.

Structural and Chemical Consequences of Intramolecular N(O)← Te Coordination in Organotellurium Compounds

Abstract The structural characteristics of organotellurium compounds possessing intramolecular coordinate N← Te and O← Te bonds are systematised and critically analysed. Particular emphasis has been placed on the enhancement of the stability and the description of the characteristic reactivity of compounds with this type of bond.

Synthesis and structure of β-tellurovinylcarbonyl compounds

Abstract By coupling β-chlorovinylcarbonyl compounds or β-acylvinyltriethylammonium chlorides with arene (alkene) tellurolates and lithium telluride β-organyltellurovinyl aldehydes, ketones I and bis(β-acylvinyl) tellurides II correspondingly have been prepared. β-Methyltellurovinyl aldehyde VI is readily oxidized by halogens, giving rise to previously undescribed β-methyldihalogenotellurovinyl aldehydes IX, which convert to the respective β-halogenotellurenylvinyl aldehydes X via elimination of a molecule of methyl halogenide. Regardless of the initial configuration at the Cβ center of the β-chlorovinylcarbonyl compounds, the nucleophilic vinylic substitution reaction results in the formation exclusively of Z-isomers of β-organyltellurovinyl aldehydes and ketones. The stereochemical outcome of this reaction is explained in terms of the addition—elimination mechanism of the nucleophilic vinylic substitution reaction, as a consequence of strong stabilization of the intermediate carbanions XVIII by intramolecular coordination of O → Te bonds. For the same reason, nucleophilic addition of arenetellurolate anions to a triple bond of α-acetylenic aldehydes and ketones occurs stereospecifically, affording exclusively Z-(β-aryltellurovinylcarbonyl) diastereomers. The crystal and molecular structures of β-(4-ethoxyphenyltelluro)-β-phenylpropenal Ip and its N-(4-methylphenyl) imine V have been studied by X-ray. Both compounds exist in the crystal as Z-diastereomers, the tellurium centers possessing a T-shaped configuration due to the formation of intramolecular coordination corresponding to O → Te (2.725 A) and N → Te (2.771 A) bonds.

Synthesis and structure of diorganyldiaryloxytelluranes with intramolecular Te ⋯ N coordination bonds

Abstract A wide series of diorganyldiaryloxytelluranes having an azomethine function in the position ortho to the tellurium atom have been synthesized by the reaction of diorganyldimethoxytelluranes with benzylidene- o -aminophenols. The X-ray structural investigation of the dimethylbis[2-(4-nitrobenzylideneimino)phenyloxy]tellurane indicates the presence of an intramolecular coordination bond Te ⋯ N. According to the dipole moment data and the 1 H, 125 Te, 14 N NMR spectra, in compounds VII, excluding those having nitro groups in the position para to the CHN bond, the Te ⋯ N coordination is retained in a non-polar solvent (benzene).

Tellurium-Containing Heterocycles with Two Heteroatoms

Publisher Summary The starting point of tellurium organic chemistry dates back to 1840 when the first representative of tellurium-containing organic compounds, diethyl telluride, was synthesized by Woehler. The rapid development of organotellurium chemistry in the past decades has been accompanied by an equally rapid expansion of another domain that relates to heterocyclic compounds, containing in the ring an additional heteroatom. The procedures for the preparation of tellurium-containing heterocycles and their reactivity display some characteristic peculiarities in comparison with sulfur and selenium analogs. These are caused by the specificity of the electronic structure and chemical behavior of the tellurium containing centers. Tellurolate anions possess the highest nucleophilicity in the series of analogous chalcogen derivatives. The same is true for diorganyl tellurides compared to their respective diorganyl sulfides and selenides. The chapter also reviews the synthesis and reactions of six-membered and five-membered tellurium-containing heterocycles.

Peculiarities in the Reactivity of Telluriumorganic Compounds in Comparison with their Sulfur and Selenium Analogs

Abstract The distinctive features of the telluriumorganic compounds′ reactivity compared to their sulfur and selenium analogs are reviewed and generalized.

Six-Membered Heterocycles with a Tellurium Atom

Publisher Summary This chapter reviews the recent developments in the preparation and reactions of six-membered tellurium-containing heterocycles, in particular those related to heteroaromatic tellurium-containing cations. Organotellurium compounds display certain characteristic peculiarities of structure and reactivity in comparison with their sulfur and selenium analogs. These peculiarities are caused by low C–Te bond energy values in various types of compounds, the tendency of dicoordinate tellurium compounds to undergo oxidative addition reactions, enhanced halogenophilicity of the RTe - anions, high electrophilicity of the TeX 3 , (X = Hal) groups, and thermodynamic stability of derivatives of tetracoordinate tellurium. Such distinctive properties of organotellurium compounds often result in marked differences in the methods of preparation of tellurium-containing heterocycles in comparison with their sulfur and selenium analogs. A number of standard procedures developed for the synthesis of the latter fail to afford tellurium-containing heterocycles when based on similar organotellurium precursors. At the same time the distinctive features of organotellurium compounds make it possible to employ for the preparation of tellurium containing heterocycles reactions that are uncommon to the chemistry of organosulfur and organoselenium compounds.

Diorganyl Derivatives of Tellurium(IV) (σ-Telluranes of R2TeX2 Type)

Abstract Literature data concerning the synthesis and reactions of diorganyl derivatives of tellurium(IV) (σ-telluranes of R2TeX2 type) are systematized and generalized in this review.

Synthesis and Reactions of Diorganyl Tellurides

Abstract Literature data concerning the synthesis and reactions of diorganyl tellurides, viz., dialkyl, alkyl aryl and diaryl tellurides are systematized and generalized in this review.