Copper selenocyanates

Kilmartin and Wright [97K1L/WRI] recently studied the development of thin CuSeCN(s) layers on metallic copper in 0.1 M SeCN solutions by cyclic voltammetry. The peaks observed were assumed to relate to the formation and removal of CuSeCN(s) according to the reaction Cu(cr) + SeCN CuSeCN(s) + e . The shapes of the volt-ammograms do, however, indicate that the electrode reaction exhibits non-Nemstian behaviour. The authors also noted that during their experiments, a possible formation of elemental selenium occurred on the electrode surface. Therefore, the recorded electrode potential characteristics cannot be regarded as well established and these data cannot be used for calculating the standard electrode potential of the above redox couple and the solubility product of CuSeCN(cr). 

Kullberg [74KUL] found it impossible to study the aqueous Cu -SeCN system since a brown precipitate was immediately formed upon addition of selenocyanate ions to a copper(ll) solution. Toropova [56TOR] prepared CuSeCN(s) by adding KSeCN to a solution of copper(l) sulphite or thiosulphate complexes, and tried to study the complex formation by measuring the solubility of CuSeCN in selenocyanate solutions. The experiment failed since the complexes initially formed were found to decompose into elementary selenium and copper(l) cyanide compounds. 

In conclusion, the review finds that no sound information on the thermodynamic properties of copper selenocyanates is available. 

The compound CuSeCN(cr) is without doubt sparingly soluble in water, and additions of Cu can be used to scavenge SeCN ions from crude oil processing waters and wastewaters [97MAN/GAL]. With time, however, it seems to decompose into Se(cr) and CuCN(aq). 

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Copper Selenocyanate is a brown precipitate obtained by precipitating copper sulphate with potassium selenocyanate. It is rapidly... 

GOL/SKO2] Golub, A. M., Skopenko, V. V., Copper selenocyanates, Russ. J. 

K1L/WR1] Kilmartin, P. A., Wright, G. A., Copper selenocyanate formation on the copper anode, Aust. J. Chem., 50, (1997), 321-327. Cited on page 297. 

The copper derivative, [CH3.CO.C(SeCN) C(CH3)0-] < Cu, occurs when an excess of aqueous 5 per cent, copper acetate is mixed with the selenocyanate dissolved in 25 parts of chloroform or benzene. The product is pale blue, insoluble in water, benzene, acetone or alcohol, and decomposed by acetic acid or aqueous sodium hydroxide. 

Two representative examples of this behavior are reflected in two distinct different chemical systems, namely (a) copper deposition from an acid sulfate electrolyte containing the co-inhibitors PEG-C1 and a bi-functional catalytic species SPS-C1 [12, 136, 243, 264] and (b) silver deposition from a cyanide electrolyte where inhibition is provided by adsorption of silver cyanide species and catalysis is achieved through adsorption of selenocyanate, SeCN [72-75]. Similar behavior is evident in some electrolytes used for the deposition of bright soft gold films [121, 180, 255-261, 267]. 

The generality of the CEAC mechanism has been demonstrated by extension to at least two other chemical systems, selenocyanate catalyzed silver deposition from a cyanide electrolyte [72-75] and iodine catalyzed CVD of copper from Cu(I)(hfac) (vtms) and related compounds [15, 77]. As shown in Figure 2.40, a one-to-one correlation between the SeCN-coverage and the silver deposition rate was established... 

MAN/GAL] Manceau, A., Gallup, D. L., Removal of selenocyanate in water by precipitation characterization of copper-selenium precipitate by X-ray diffraction, infrared, and X-ray absorption spectroscopy, Environ. Sci. Technol., 31, (1997), 968-976. Cited on page 297. 

With other halides, the reaction is conveniently performed by treatment of the alkylthdlium compound with the appropriate copper(I) halide. The product yield is increased by the addition of potassium halide.jhe thallium moiety can also be replaced by other groups, similarly to the arylthallium compounds. The cyano group is introduced by reaction with copper(I) cyanide.lSi the thiocyano group by reaction with potassium and/or copper thiocyanate>5i.i52 and the selenocyano group by treatment with potassium selenocyanate. 

When diallyl ether (40) is reacted with potassium selenocyanate, copper(II) chloride, and methanol a mixture of 3,5-bis(methoxymethyl)-1,4-oxaselenane (41) and 3-methoxymethyl-6-methyl-l,4-oxaselenepane (42) is formed. The amount of the selenane increases with reaction time and the ratio of products is also affected by variations in temperature. These facts suggest that an equilibrium exists, linking the products through an intermediate episelenonium cation (43) (Scheme 16) <79JCS(P1)1206>. 

ALKENES Allyl dimethyldithiocarbamate. Bis(t -cyclopentadienyl)niobium trihydride. Cyanogen bromide. Di-n-butylcopperlithium. a,o-Dichloromethyl methyl ether. 2,3-Dimethyl-2-butylborane. N,N-Dimethyl dichlorophosphoramide. Diphenyl diselenide. Di-n-propylcopperlithium. Ferric chloride. Grignard reagents. Iodine. Lithium phenylethynolate. Lithium 2,2,6,6-tetramethylpiperidide. Methyl iodide. o-Nitro-phenyl selenocyanate. Propargyl bromide. rra s-l-Propenyllithium. Selenium. Tetrakis(triphenylphosphine)palladium. Titanium(IH) chloride. Titanium trichloride-Lithium aluminum hydride. p-Toluenesulfonylhydrazine. Triphenylphosphine. Vinyl-copper reagents. Vinyllithium. Zinc. 

Other Systems.—An oxaselenepan (195) is formed as the primary product by intramolecular oxyselenation in the reaction of diallyl ether with potassium selenocyanate in methanol, in the presence of copper(ii) chloride.A range of... 

The benzo-l,2-selenazine (benzisoselenazine) ring system 144 can be prepared by copper(l)-promoted reaction of amine 143 with potassium selenocyanate in the presence of triethylamine (Equation 37) <2000JOC8152>. The ring closure also affords 3,3-dimethylindoline as a by-product, but a twofold excess of selenocyanate and acetonitrile as a solvent led to optimum formation of the desired selenazine. 

Related Reagents. Copper(II) Chloride Copper(II) Chloride-Copper(II) Oxide lodine-Copper(II) Chloride Copper(I) Chloride-Oxygen Copper(I) Chloride-tetrabutylammonium Chloride Copper(I) Chloride-Sulfur Dioxide lodine-Alutninum(III) Chloride-Copper(II) Chloride lodine-Copper(I) Chloride-Copper(II) Chloride Methylmagnesium lodide-Copper(I) Chloride Palladium(II) Chloride-Copper(I) Chloride Palladium(II) Chloride-Copper(II) Chloride Phenyl Selenocyanate-Copper(II) Chloride nyl-magnesium Chloride-Copper(I) Chloride Zinc-Copper(I) Chloride. 

Thiolates and selenocyanates displace halogen from ArHal with a palladium(o) compound and copper(i) iodide, respectively, as catalysts. 

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