Dimethyl ditelluride

As with selenium analysis, HGAAS also finds a place in Te determination. Basnayake et al. amended cultures of P. fluorescens K27 with 0.1 mM tellurite and, after 92-h growth, determined that approximately 34% of added Te was present as either precipitated, elemental Te in/or on centrifuged cells the balance of added Te remained in solution.190 In this same study, GC/MS was used for determination of DMTe in the same facultative anaerobe amended with tellurate.190 Earlier, GC/MS was used to analyze the headspace of a tellurium-resistant fungus amended with tellurite.215 This last is one of the few reports of the detection of dimethyl ditelluride in microbial headspace (see below). 

Dimethyl ditelluride (typicalprocedure. Clean Na metal (3.2 g, 0.14 mol) is added to 100 mL of liquid NHj at 78°C. After stirring for 1 h, high-purity powdered Te (18.2 g, 0.14 mol) is added in 0.5 g portions. Methyl iodide (24 g, 0.17 mol) is then added dropwise for 20 min, with stirring, to the dark green solution. The NHj is evaporated, H2O is added to the residue and the mixture extracted with ether (4X50 mL). The combined deep red extracts are dried overnight (CaCy, and evaporated under vacuum. The residue is then distilled (7.6 g (38%) b.p. 97°C/9 torr). 

Drew (J. Chem. Soc., 1929, p. 568) considers that the /5-dihalides do not give dimethyl telluride on reduction, but an orange oil of carbylamine odour, probably dimethyl ditelluride. 

The filtrate from the iodide on evaporation in a desiccator yields a colourless crystalline solid (1 3 grams). Extraction with small quantities of hot water gradually removes any remaining iodide, a white powder remaining as residue. This is an anhydride of methyl hydroocytellurium oxide (telluracetic acid), CH3.TeO.OH, which cannot be obtained pure. In aqueous solution it is neutral to litmus, gives no precipitate with silver nitrate, and is reduced by potassium bisulphite to dimethyl ditelluride. It has a persistent odour, and gradually blackens above 230° C. 

From the point of view of the hetero-atom itself, there are two more known below selenium in the Periodic Table. Each deserves some special comment. The next atom, directly below selenium, is tellurium. It is more metallic, and its compounds have a worse smell yet. I heard a story about a German chemist, many years ago, who was carrying a vial of dibutyl telluride in his pocket in a passenger coach from here to there in Germany, back at about the turn of the century. It fell to the floor and broke. No one could remain in the car, and no amount of decontamination could effectively make the smell tolerable. Scratch one railway coach. But the compound, 2C-TE, would be readily makeable. Dimethyl ditelluride is a known thing. 

Tetrabromocyclopropene (21) reacted very readily with dimethyl diselenide and with dimethyl ditelluride to give the tris(methylchalcogeno)cyclopropenylium tribromidcs 22 in high yield. The reaction with dimethyl disulfide was slower but also afforded the tris(methylsulfanyl)cyclo-propenylium salt in high yield. 

A solution of dimethyl ditelluride (0.397 g, 1.5 mmol) in CH2CI2 (5 mL) was added dropwise to a stirred solution of tetrabromocyclopropene (0.356 g, 1.0 mmol) in CHjCl, (10 mL) at rt. The immediately formed greenish yellow powder was filtered, washed with a small amount of CH2CI2, then vacuum dried yield 0.736 g (94%) mp >250 = C (dec.). 

For MMA polymerization with X=TeMe, Yamago a al. synthesized low-polydispersity polymers (Mw/M 1.15) by the addition of a small amount of dimethyl ditelluride (MeTe)2, without which Mw/Mn exceeded 1.35 due to a small Cex (e.g., 3.6 at 60° C ). This suggests an inaease of k a in the presence of (MeTe)2. A kinetic study on the role of (MeTe)2 demonstrated that (MeTe)2 worked as an efficient deactivator of P to in situ generate MeTe (and P-TeMe), and MeTe" then worked as a highly reactive activator of the dormant species P-TeMe. Namely, there is a rapid reversible activation-deactivation process mediated by (MeTe)2, that is, P-TeMe+MeTe" P" + (MeTe)2 as another activation mechanism besides E)T, accounting for the observed dramatic improvement of the polydispersity controllability. 

Diheteroatom compounds, such as dimethyl ditelluride, diphenyl ditelluride, tetramethyl distibine, tetraphenyl distibine, and 2,6-dimesitylphenylthiodiphenylbismuthine 2 (Scheme 5), were used as cocatalysts to increase the MWD control. As these cocatalysts do not generate initiating radical species for the polymerization, a binary system consisting of an... 

Diphenyl ditelluride adds to alkynes upon irradiation with a tungsten lamp in the absence of solvent to give 1,2-bis(phenyltelluro)alkenes (Equation (67)).191 The ( )-isomers are obtained as the major product through a radical chain mechanism. Functionalized internal alkynes such as dimethyl acetylenedicarboxylate and dihaloalkynes XCCX (X = C1 or Br) are able to participate in the reaction.192... 

Dihydrofolate reductases (DHFR), 48, 54, 56 Dimethyl chalcogenides, 131-133 Dimethylselenide, 131-133 Dimethyltellurides, 131-133 Diorgano diselenides, 113 Diorgano ditellurides, 113 Diorganochalcogen(IV) dihalides crystallographic structure, 80f redox reactions, 90 Diorganoselenides... 

Interestingly, when 2,3 6,7-bis(trimethylene)naphthalene is treated with sodium ditelluride in HMPTA or 1,3-dimethyl-2-imidazolidinone solution,... 

Dihydrotellurophene-1,1-difluoride119 was formed in the low-temperature reaction of 2,5-dihydrotellurophene with xenon difluoride. Aryltellurium(Vl) fluoride was synthesized from diaryl ditelluride or aryltellurium(lV) fluoride120 while perfluorinated dimethyl or diphenyl tellurides are transformed only to difluorides121,122 (Scheme 51). 

Lithium triethylborohydride in THF has also been used to reduce tellurium to the ditelluride in a THF medium. Dimethyl ditellurium and diisopropyl ditellurium were prepared in 80% yield from these ditelluride solutions4. 

Diphenyltellurophene is obtained by treatment of diethyl ditelluride with diphenyldiacetylene in N2H4-KOH-DMSO-H2O at 55 °C (DMSO = dimethyl sulfoxide Scheme 17) <2002KGS280>. 

Organotellurium CTAs Te-7 and Te-8 were prepared by reacting AIBN with dimethyl- and diphenylditelluride, respectively, but in low yields (8-18%). This route has the practical advantage that both AIBN and ditellurides are stable in air and can be handled without special precautions. Furthermore, the air-sensitive CTAs formed can be directly used for polymerization without purification because the only side product is a dimer of AIBN-derived radicals, which does not affect the polymerization reaction. Despite the simplicity of this procedure, the use of purified initiators is the method of choice for obtaining living polymers with the highest level of control of MWD. 

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