Reduction of Selenium and Tellurium Compounds

Two-electron oxidations and reductions of selenium and tellurium compounds 80... 

Homogeneous crystalline alloys of selenium and tellurium, Se Tei-x, of various compositions (x = 0.1-0.9) are prepared by the co-reduction of solutions of Se(IV) and Te(IV) compounds, e.g. dialkylselenites and tetraalk-oxytelluranes (or glycol solutions of Se02 and Te02), with hydrazine. ... 

Reduction of Organoselenium and -tellurium Halides and Oxides. TUD reduces aryltellurium trihalides to diaryl ditel-lurides (eq 2) and diorganyltellurium dihalides and telluroxides to diorganyl tellurides (eq 3) in high yield. The corresponding selenium compounds are reduced similarly. Some examples are given in Table 2. The reduction is performed by premixing the substrate and 2 N NaOH at room temperature for 15 min prior to the addition of TUD in petroleum ether. 

Raney-nickel as a reagent for reductive cleavage of chal-cogen atoms from sulfur, selenium and tellurium compounds. Phosphorus, Sulfur Silicon Relat. Elem. 1978 4(3) 259-265. 

Metal ions such as arsenic(Ill), selenium and tellurium (Me"" ) may be determined by stripping voltammetry after adding a second metal, such as copper (Me h ), to the test solution and co-electrolysing the two metals onto the surface of the HMDE. The copper acts as a co-deposition agent and facilitates the deposition of the analyte, Me . on the electrode surface as an inter-metallic compound. The analyte may then be stripped from the electrode either by oxidation (ASV) or by further reduction (CSV) to an anionic species according to the following reaction scheme. 

In spite of the fact that the above mechanism for formation of organometallic compounds during electrolysis of nitriles appears most probable to us, it is impossible not to mention another possible explanationfor this reaction. In electrochemical reduction of acrylonitrile organometallic compounds have been obtained from tin, sulfur, selenium, and tellurium, which are themselves reduced electrochemically. 

The question arises as to whether the formation of organometallic compounds during electrolysis of aqueous solutions of acrylonitrile is not due to cyanoethylation of hydrides formed initially at the electrode. In Table 5 data on the electrochemical reduction of tin, sulfur, selenium, and tellurium in aqueous solutions of sodium sulfate with and without acrylonitrile are compared [40]. 

The induced co-deposition concept has been successfully exemplified in the formation of metal selenides and tellurides (sulfur has a different behavior) by a chalcogen ion diffusion-limited process, carried out typically in acidic aqueous solutions of oxochalcogenide species containing quadrivalent selenium or tellurium and metal salts with the metal normally in its highest valence state. This is rather the earliest and most studied method for electrodeposition of compound semiconductors [1]. For MX deposition, a simple (4H-2)e reduction process may be considered to describe the overall reaction at the cathode, as for example in... 

Wolfolk CA, Whiteley HR. 1962. Reduction of inorganic compounds with molecular hydrogen by Micrococcus lactilyicus. I. Stoichiometry with compounds of arsenic, selenium, tellurium, transition and other elements. J Bacteriol 84 647-58. 

Complexes of both selenium(IV) and tellurium(IV) with sulfur-containing ligands are known although the structural properties appear to have been determined only for the tellurium(IV) species. However, due to the smaller size of selenium(IV) and its poorer acceptor properties, as compared with tellurium(IV), its maximum coordination number appears to be six whilst it has been found to be eight for tellurium.78 Furthermore, the greater tendency of tellurium to form secondary bonds may cause the structures of similar selenium(IV) and tellurium(IV) compounds to be different. 9 It is also pertinent to note that the reduction of tellurium(IV) to... 

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