Complex selenium oxides

Hayes, KF. Papelis, C. Leckie, J.O. (1988) Modeling ionic strength Effects on anion adsorption at hydrous oxide/solution interfaces. J. Colloid Interface Sd. 78 717—726 Hayes, KF. Roe, A.L. Brown, G.E. Hodgson, KO. Leckie, J.O. Parks, G.A. (1987) In-situ X-ray absorption study of surface complexes Selenium oxyanions on a-FeOOH. Sdence 238 783-786... 

Hayes, K.F., L.A. Roe, G.E. Brown, Jr K.O. Hodgson, J.O. Leckie, and G.A. Parks. 1987. In-silu x-ray absorption study of surface complexes at oxide/water interlaces . Selenium oxyanions on [Pg.252]

The electrodeposition of copper indium selenide and telluride was discussed by Bhattacharya and Rajeshwar (66). The deposition solutions were made in a multistep process. A 0.5 M solution (A) of indium chloride was prepared. The copper solution (B) was prepared from cuprous chloride dissolved in 30 ml of triethanolamine, 40 ml of 30% ammonia and 150 ml of water. The copper concentration was 0.5 M. Solutions A and B were mixed in equal amounts, diluted 10 times and adjusted to pH 1 with HCI. This solution (C) was aged for 24 hrs. The actual deposition bath was made from 20 ml of either 0.1 M selenium oxide or 0.1 M tellurium oxide and 60 ml of solution C. The triethanolamine was added to the copper solution as a complexing agent to shift the deposition potential. Depositions were carried out at -1.0 volt versus a saturated calomel electrode. The initial current density was 12 mA/cm . 

Grundnes, J. and Klaeboe, P. (1964) Spectroscopic studies of charge-transfer complexes. XII. Diphenyl selenium oxide and iodine. Acta Chem. Scand., 18, 2022-2028. 

The solution should be free from the following, which either interfere or lead to an unsatisfactory deposit silver, mercury, bismuth, selenium, tellurium, arsenic, antimony, tin, molybdenum, gold and the platinum metals, thiocyanate, chloride, oxidising agents such as oxides of nitrogen, or excessive amounts of iron(III), nitrate or nitric acid. Chloride ion is avoided because Cu( I) is stabilised as a chloro-complex and remains in solution to be re-oxidised at the anode unless hydrazinium chloride is added as depolariser. 

A method to circumvent the problem of chalcogen excess in the solid is to employ low oxidation state precursors in solution, so that the above collateral reactions will not be in favor thermodynamically. Complexation strategies have been used for this purpose [1, 2]. The most established procedure utilizes thiosulfate or selenosulfate ions in aqueous alkaline solutions, as sulfur and selenium precursors, respectively (there is no analogue telluro-complex). The mechanism of deposition in such solutions has been demonstrated primarily from the viewpoint of chemical rather than electrochemical processes (see Sect. 3.3.1). Facts about the (electro)chemistry of thiosulfate will be addressed in following sections for sulfide compounds (mainly CdS). Well documented is the specific redox and solution chemistry involved in the formulation of selenosulfate plating baths and related deposition results [11, 12]. It is convenient to consider some elements of this chemistry in the present section. 

Utilizing low-oxidation selenium precursors appears to be particularly suited for obtaining single-phase ZnSe deposits. Results have been presented of ZnSe electrosynthesis from alkaline selenosulfate solutions of complexed Zn(II) [108]. 

Perspectives for fabrication of improved oxygen electrodes at a low cost have been offered by non-noble, transition metal catalysts, although their intrinsic catalytic activity and stability are lower in comparison with those of Pt and Pt-alloys. The vast majority of these materials comprise (1) macrocyclic metal transition complexes of the N4-type having Fe or Co as the central metal ion, i.e., porphyrins, phthalocyanines, and tetraazaannulenes [6-8] (2) transition metal carbides, nitrides, and oxides (e.g., FeCjc, TaOjcNy, MnOx) and (3) transition metal chalcogenide cluster compounds based on Chevrel phases, and Ru-based cluster/amorphous systems that contain chalcogen elements, mostly selenium. 

The first examples of mononuclear disulfur and diselenium complexes of platinum have been described.330 Reduction of the sterically hindered complex trans- PtC 2( P M e2A r)2] (Ar = 2,4, 6-tris[bis(trimethylsilyl)methyl]phenyl, 2,6-bis[bis(trimethylsilyl)-methyl]-4-[tris(trimethylsilyl) methyl]-phenyl) with lithium naphthalide in THF solution affords the platinum(0) species [Pt(PMe2Ar)2]. Oxidative addition of elemental sulfur or selenium yields the dichalcogenatoplatinum(II) complexes of the type [PtE2(PMe2Ar)2] (E = S, Se) containing a unique PtE2 ring system. The complexes are stable to air in the solid state, but slowly decompose in solution after several days at room temperature. 

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