Tellurenyl compounds

Although these tellurenyl compounds are representative tellurenylating reagents, their synthetic utility is not as high as that of the corresponding selenenyl compounds. 

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Benzo-l,2,3-telluradiazolium perchlorate 87 is the only compound known so far containing a 1,2,3-telluradiazole ring. It was obtained in 65% yield by reaction of the tellurenyl chloride 88 with silver perchlorate (88KGS1426). 

This group of compounds is represented by A-methyl-2,5-diphenyl-l-aza-6-oxa-6fl-tellurapentalene 94 which was prepared in low yield (11%) by coupling an imidoyl chloride 95 with a tellurenyl chloride 96 in acetonitrile solution containing 2,6-lutidine (87MI2). 

Organotellurium(II) compounds can also contain a three-center, four-electron bond as shown for 39 to 42 in Fig. 19. Typically, these molecules contain an odd number ligands around the central atom and an electronegative atom helps to stabilize a tellurenyl halide or selenenyl halide bond through chelation to form a four, five, or six membered ring. " Such molecules are described as lO-Te-3 and lO-Se-3... 

Halogenated derivatives of tellurium in the oxidation state +2, namely tellurenyl halides, are unfamiliar compounds compared to the well-known selenium analogues. 

These compounds are in principle easily accessible by the controlled halogenolysis of the parent ditellurides. However, the first compound obtained in 1959, 2-naphthyl-tellurenyl iodide, remained for a long time the only stable representative of this class until the preparation of other members of this class by a successful use of the same method." ... 

From alkynyl Grignard and lithium compounds and organyl tellurenyl halides... 

Organo tellurium halides, also named organo tellurenyl halides, are in principle easily accessible through controlled halogenolysis of diorgano ditellurium compounds. However, 2-naphthyl tellurium iodide, prepared in 19592 from bis[2-naphthyl] ditellurium and iodine, remained the only compound of this type until 1971/72, when a series of ortho-carbonyl substituted phenyl tellurium halides were synthesized3-4. Aryl tellurium halides without substituents in the ortho-position to tellurium were isolated and characterized in 1975s. 

Contrary to expectations, the reactions of tellurenyl chlorides 2 with bromine as well as tellurenyl bromides 16 with chlorine do not afford non-symmetric /i-trihalogenotellurovinylcarbonyl compounds, but various mixtures of tellurium trichlorides 17 and tellurium tribromides 18 (86JOC1692). For example, tellurenyl chloride 2a reacts with bromine to give a 1 2 mixture of tellurium trichloride 17a and tellurium tribromide 18a. Under the same conditions treatment of tellurenyl bromide 16a with chlorine gives a mixture of the same trihalides, but in a 2 1 ratio (Scheme 9). 

Reactions of aromatic aldehydes and ketones containing a tellurenyl halide group in an o-position with organometallic compounds provide an approach to less accessible o-alkyltellurocarbonyl compounds (72BSF3559, 78T655, 81JOM(208)11) (Scheme 14). 

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