From Aryl Tellurium Trihalides by Reduction

Generally, the reduction of aryl tellurium trihalides by a variety of reducing agents leads to diaryl ditellurium compounds. However, the reduction of aryl tellurium trihalides with stabilizing groups in the or//to-position to the tellurium atom, by sodium hydrogen sulfite, disodium disulfite, or hydrazine hydrate to aryl tellurium halides shows that the reduction can be stopped at the tellurium halide stage. 

2-Nitropbenyl Tellurium Bromide 0.42 g (6 mmol) of solid sodium hydrogen sulfite are added over a period of 20 min to a stirred suspension of 1.0 g (3 mmol) of 2-nitrophcnyl tellurium tribromide in water at 0°. The resultant deep-red slurry is stirred for 20 min at 0 , filtered, the red paste is dissolved in dichloromethane, filtered again, and the dichloromethane solution is diluted with hexane. The product crystallizes as a deep-red solid yield 0.59 g (80%) m.p. 76 . 

2-Phenylazophenyl Tellurium Chloride 3.5 g (8.4 mmol) of 2-phenylazophenyl tellurium trichloride are dissolved in 50 ml of refluxing methanol. A solution of 0.5 g (10 mmol) of hydrazine hydrate in 50 ml of 

Al-Salim, A.A. West. W.R. McWhinnie, T.A. Hamor, J. Chem. Soc., Dalton Trans. 1988, 2363. 

A melting point of 125 was found for the same compound prepared in the same way . These two compounds that had the same elemental composition were postulated to be polymorphs.  

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