Potassium ruthenate

Potassium ruthenate, /ra s-Kj[Ru(0H)j(0)3] The deep red potassium salt was first made by Klaus in 1844 (published in 1845) [1, 2], It was later made by fusion of Ru metal with KOH and KNO3 followed by extraction with water and crystallization, methods used also by subsequent workers [456, 523], A dark green form which contains tetrahedral [RuO ] (see below) was made by fusion of RuO with KO at 780°C for 45 days [524], MO orbital energy levels for the anion were calculated using the Wotfsberg-Helmholtz method [523],... 

The reversibility of the [RuO ] - [RuO ] couple cf. 1.4.1.3) and the Raman spectrum of ruthenate in aqueous base suggest that it is tetrahedral, [RuO ] , in solution. Thus, unlike RuO and [RuO ] , ruthenate changes the structure of its anion from that of the trigonal bipyramidal fra 5-[Ru(0H)3(0)3] in the solid potassium and barium salts to tetrahedral [RuO ] in solution. There is evidence from electronic spectra of potassium ruthenate doped into K CrO and K SeO and of barium ruthenate doped into BaSO, BaCrO and BaSeO that, in that these enviromnents at least, the Ru is tetrahedrally coordinated [533]. 

Electronic spectra (Table 1.1, Fig. 1.2) have been measnred for the orange soln-tions of (RuO ] in aqueous base from 250-600 nm. [212-215, 222], and reproduced [215, 222]. There are two at 460 and 385 nm. [212, 213, 222] or three bands in the visible-UV region, at 460, 385 and 317 nm [214, 215]. These appear to be at the same positions as those for [RuO ] but the intensities and hence the general outline of the two spectra are very different. Woodhead and Fletcher reviewed the published molar extinction coefficients and their optimum values / dm (mol" cm" ) are 1710 for the 460 nm. band, 831 for the 385 nm. band and 301 for the 317 nm. band - the latter band was not observed by some workers [214]. The distinctive electronic spectrum of ruthenate in solution is useful for distinguishing between it, [RuO ]" and RuO [212, 222]. Measurements of the electronic spectra of potassium ruthenate doped in K CrO and K SeO and of barium ruthenate doped into BaSO, BaCrO, and BaSeO (in all cases the anions of these host materials are tetrahedral) indicate that in that these environments at least the Ru is tetrahedrally coordinated. Based on this evidence it has been suggested that [RuO ] in aqueous solution is tetrahedral [RuO ] rather than franx-[Ru(0H)3(0)3] [533, 535]. Potential modulated reflectance spectroscopy (PMRS) was used to identify [RuO ] and [RuO ] " in alkaline aqueous solutions during anodic oxidation of Ru electrodeposited on platinum from [Ru3(N)Clg(H30)3] [228]. 

The orange-colored solution, containing, among other things, potassium ruthenate, was treated with nitric acid, whereupon a black precipitate of osmium dioxide containing from fifteen to twenty per cent of ruthenium oxide was thrown down as a velvety deposit. Klaus distilled this with aqua regia, taking care to condense the osmium tetroxide. The residue... 

Lead tetraacetate-Manganese(II) acetate, 157 Osmium tetroxide, 222 Potassium ruthenate, 259 Samarium(II) iodide, 270 reagents specific for primary alcohols Osmium tetroxide, 222 reagents specific for benzylic alcohols Cetyltrimethylammonium permanganate, 69... 

Methoxy-2,2,6,6-tetramethyl-1 -oxopiperidinium chloride, 183 Pyridinium chlorochromate-Benzotria-zole, 262 of amines to nitro compounds Dimethyldioxirane, 120 other nitrogen compounds /-Butyl hydroperoxide-Dichlorotris-(triphenylphosphine)ruthe-nium(II), 54 Di-/-butylimoxyl, 94 Potassium ruthenate, 259 Ruthenium tetroxide, 268 of aromatic side chains Trimethylsilyl chlorochromate, 327 of diols... 

Potassium ruthenate, 259 Dienals (see Unsaturated carbonyl compounds)... 

Methylthiomethyl p-tolyl sulfone, 192 Potassium ruthenate, 259 Trimethylsilyl chlorochromate, 327 a-Substituted ketones (see also Halo carbonyl compounds, Hydroxy aldehydes and ketones) a-Acetoxy ketones Benzeneselenenyl chloride-Silver acetate, 27... 

Potassium ruthenate, 259 Ruthenium(III) chloride, 268 Ruthenium (III) chloride-Sodium periodate, 105... 

Catalytic potassium ruthenate (K2Ru04) in the presence of potassium peroxodisulfate (K2S20g) and Adogen 464 under phase-transfer conditions146... 

Ruthenium Dioxide (by Pichler).190 A mixture of 1 g of ruthenium powder, 10 g of potassium hydroxide, and 1 g of potassium nitrate is fused in a silver (or a nickel) crucible. It is recommended that the potassium nitrate be added not simultaneously but in portion after portion. In 1-2 h the fusion is complete. After cooling, the mass is dissolved with water into a solution. The dark red solution of potassium ruthenate is heated to boiling, and methanol is added to this dropwise. Immediately after the first drop of methanol has been added, the reduction of the ruthenate to ruthenium dioxide takes place and the reduction is completed in a few minutes. After leaving the precipitate for 1-2 h, the precipitate is collected on a glass filter, washed 7 times with a dilute nitric acid solution and then 18 times with distilled water, and dried at 110°C for 24 h in a desiccator. Pichler s dioxide thus prepared does not show any distinct diffraction patterns corresponding to the oxide of ruthenium and is partly soluble into hot concentrated hydrochloric acid. These facts suggest that Pichler s dioxide is a mixture of the oxide and the hydroxide of ruthenium.191... 

It now remains to separate out the ruthenium. This is accomplished by fusing with potassium hydroxide and nitrate, best in a silver crucible, and subsequently dissolving in water. The solution obtained has an orange-yellow colour in consequence of the presence of potassium ruthenate. This colour is removed by the addition of nitric acid, ruthenium oxide separating out. Ignition in a graphite crucible with a little chalk yields the free ruthenium, the chalk combining with any silicon, chromium, and osmium that may have been present. 

Alkali hypochlorites effect the solution of ruthenium when fused, but the best mixture to employ consists of potassium hydroxide and nitrate, a green mass of potassium ruthenate. K2P.u04, being formed. This dissolves in water to an orange-coloured solution, which leaves a black stain upon the skin. 

The dioxide may also be obtained by heating the sulphate or disulphide in the presence of air. It crystallises in the form of hard, tetragonal pyramids, of density 7-2, and isomorphous with cassiterite and rutile.2 The crystals exhibit a green iridescent metallic lustre. They are not acted upon by acids, but yield potassium ruthenate when fused with potassium hydroxide. 

In solution potassium ruthenate is of a deep orange colour, but in dilute solution assumes a green colour, due to formation of per-ruthenate. Hydrochloric acid effects the precipitation of an oxide, chlorine being simultaneously evolved. The solution stains the skin black owing to separation of oxide. 

The melt formed by fusion of ruthenium in potassium hydroxide and nitrate, and thus containing potassium ruthenate, was dissolved in water and boiled with potassium cyanide. The orange colour wa quickly bleached, the ruthenocyanide produced being subsequently isolated by crystallisation. 

Detection of Ruthenium in Platinum Alloys.—In order to detect the presence of ruthenium in platinum alloys, a portion of the alloy is fused with lead. The melt is extracted with nitric acid and the residue ignited in contact with air in order to volatilise the osmium. The mass may now contain platinum, iridium, rhodium and ruthenium, and is fused with potassium nitrate and hydroxide. The whole is dissolved in water, treated with excess of nitric acid and allowed to stand in a flask covered with filter-paper. In a few hours (12-24) the filter-paper darkens if ruthenium is present, in consequence of the evolution of vapour of its tetroxide. To confirm the presence of ruthenium, the paper is ignited and the ash fused with potassium nitrate and hydroxide. On extraction with water the orange colour of potassium ruthenate is obtained.1... 

Potassium naphthalenide, 122, 431 Potassium permanganate, 360, 388-391 Potassium ruthenate, 391 Potassium selenophenolate, 433... 

Potassium ruthenate, K2RUO4, is prepared in situ from ruthenium trichloride and aqueous persulfate. The reagent catalyzes persulfate oxidations of primary alcohols to acids, secondary to ketones, and primary amines to nitriles or acids at room temperature in high yields [196],... 

Sodium ruthenate [957] and potassium ruthenate [196 oxidize allylic and benzylic alcohols to carboxylic acids at room temperature. Cinnamyl alcohol is transformed into cinnamic acid with sodium ruthenate in 1 M sodium hydroxide at 10 °C after 1 h in 70% yield [957]. In oxidations with potassium ruthenate, only catalytic amounts can be used in the presence of a persulfate, which reoxidizes the reduced ruthenium salt [196. ... 

The unusual oxidant nickel peroxide converts aromatic aldehydes into carboxylic acids at 30-60 °C after 1.5-3 h in 58-100% yields [934. The oxidation of aldehydes to acids by pure ruthenium tetroxide results in very low yields [940. On the contrary, potassium ruthenate, prepared in situ from ruthenium trichloride and potassium persulfate in water and used in catalytic amounts, leads to a 99% yield of m-nitrobenzoic acid at room temperature after 2 h. Another oxidant, iodosobenzene in the presence of tris(triphenylphosphine)ruthenium dichloride, converts benzaldehyde into benzoic acid in 96% yield at room temperature [785]. The same reaction with a 91% yield is accomplished by treatment of benzaldehyde with osmium tetroxide as a catalyst and cumene hydroperoxide as a reoxidant [1163]. 

More intensive dehydrogenation of primary amines having two hydrogen atoms on the adjacent carbons leads to nitriles. Such dehydrogenations are accomplished by argentic oxide cobalt peroxide [1136], nickel peroxide [936], lead tetraacetate [443, 444], sodium hypochlorite [692], potassium ferricyanide [924], and potassium ruthenate [196] (equation 513). 

The tetroxides of ruthenium and osmium are solids of low m.p. (RUO4, 25°. OSO4, 41°). R11O4 volatilises when a stream of Clg is passed through an alkaline solution of a ruthenate and is conveniently prepared by oxidising potassium ruthenate with periodic acid (Martin, 1952) ... 

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