Potassium ferrate, preparation

The best known oxoanion of iron is the ferrate(VI) prepared by oxidizing a suspension of hydrous iron(III) oxide in concentrated alkah with potassium hypochlorite or by anodic oxidation of iron in concentrated alkah. Crystals of potassium ferrate [13718-66-6], K FeO, are deep purple, orthorhombic, and contain discrete tetrahedral [FeOJ anions. Barium ferrate [13773-23A] can be precipitated from solutions of soluble ferrate salts. 

An impure sample of potassium ferrate, K2Fe04, may be prepared as follows Dissolve sufficient ferric chloride, FeCl3,6H20, to correspond to 40 g. Fe(OH)3 in 2 1. of hot water and precipitate the hydroxide with potassium hydroxide. Wash the precipitate repeatedly with hot water by decantation until nearly all chlorides have been removed and evaporate the suspended hydroxide to a volume of about 65 cc., bringing it into a porcelain dish that will hold about 250 cc. Break up 25 g. of solid potassium hydroxide into small pieces and add it to the ferric hydroxide, warming the mixture to insure solution. 

Potassium ferrate (VI) has been prepared in an impure state and in low yields by the action of chlorine or bromine on hydrous iron(III) oxide suspended in potassium hydroxide solutions. The procedure described here is a modification of the chlorine oxidation method1 which facilitates the prediction of 5- to 10-g. samples of potassium ferrate (VI) in a fair state of purity and in good yield. 

If it is desirable to obtain a sample of greater purity than those prepared by the recommended procedure, the sample may be subjected to an additional reprecipitation from 6 M potassium hydroxide solution, using the same procedure as described above. Such additional purifications of samples give products ranging in purity from 98.5 to 99% potassium ferrate (VI) however, a large amount of the potassium ferrate (VI) is lost in the process. 

Potassium ferrate, K2Fe04, which is prepared from ferric nitrate and alkaline hypochlorites [916], is a selective oxidant for the conversion of primary alcohols into aldehydes (not acids), of secondary alcohols into ketones, and of primary amines into aldehydes [917, 918]. 

Sodium ruthenate, Na2Ru04, is prepared in situ from ruthenium tetroxide (in solution in carbon tetrachloride) and 1 M sodium hydroxide by shaking for 2 h at room temperature. The reagent remains in the aqueous layer, which acquires bright-orange color [937]. It oxidizes primary alcohols to carboxylic acids and secondary alcohols to ketones and is comparable with but stronger than potassium ferrate [937]. 

Thompson GW, Ockerman LT, Schreyer JM (1951) Preparation and purification of potassium ferrate VI. J Am Chem Soc 73 1379-1381... 

The preparation, analysis and properties of the potassium ferrate(VI) are given in / org.SyntA4( 1953) 164. 

While attempting to prepare an T71-(vinylcarbene)iron complex121 by the alkylation or acylation of an a,/3-unsaturated acylferrate, Mitsudo and Wa-tanabe found122 that the major isolated product was in fact an -vinylketene complex (178), formed presumably by the carbonylation of an intermediate V-vinylcarbene, which may then undergo olefin coordination to the vacant metal site. All attempts to isolate such intermediates, or to observe them by 13C NMR spectroscopy, failed. Only in the reaction between potassium tetracarbonyl -cinnamoy ferrate (179.a) and pivaloyl chloride (180.b) was a side product (181) isolated in appreciable yield. In other reactions, only a trace (<1%) of such a compound was detected by spectroscopy. The bis(triphenylphosphine)iminium(l + ) (PPN) salts of 179.a and 179.b also reacted with 2 equiv of ethyl fluorosulfonate to give 178.g and 178.h in 21 and 37% yield, respectively. All products were somewhat unstable to silica gel, hence the low isolated yields in some cases. 

Preparation and Properties of Ferrates. Put about 0.5 g of triturated potassium hydroxide (if possible, containing no carbonate) into a porcelain bowl, add 3-5 drops of an iron(III) chloride solution and 3-5 drops of bromine [in a jume cupboard ). After heating... 

To prepare potassium trioxalatoferrate(III), put 1.25 g of iron(III) sulphate, the prepared barium oxalate, 1.5 g of potassium oxalate, and 30 ml of water into a 500-ml beaker. Heat the mixture for several hours in a water bath, maintaining a constant volume. After separation of the barium sulphate precipitate, evaporate the filtrate to a volume of 5 ml and cool it. Filter off the potassium trioxalato-ferrate(III) crystals, rinse them with a small amount of water and then with ethanol, and dry them in a vacuum-desiccator over sulphuric acid. Write the equations of the reactions. 

Modeling the biological oxidation of tertiary amines, Audeh and Lindsay-Smith239 prepared perhydropyrido[l,2-a]pyrimidine by the oxidative cyclization of 3-piperidino propylamine by use of potassium hexacyano-ferrate(III) in potassium hydroxide solution. 

Prepare the reagent by mixing 10 drops 0 033m potassium hexacyano-ferrate(III) solution, 2 drops M sulphuric acid, and 6 drops 2 per cent p-pheneti-dine hydrochloride solution. 

Sodium per ferrate, Na2Fc04, may be prepared in an analogous manner to the potassium salt already described. It also results when ferric oxide is fused with sodium peroxide and the cooled mass treated with ice. Sodium perferrate then passes into solution.3... 

Strontium perferrate, SrFe04, is obtained 4 by double decomposition of the potassium salt and a saturated, neutral solution of strontium bromide. The precipitate is washed with alcohol and ether. Obtained in this manner, the strontium ferrate is not pure, but contains admixed ferric oxide. It is deep red in colour, slightly soluble in water, and readily decomposed by acids. It is useful for preparing aqueous solutions 4 of the perferrates of the less common alkali metals—lithium, rubidium, caesium—of calcium and magnesium. 

PURPOSE OP EXPERIMENT Prepare potassium tris(oxalato)ferrate(III) trihydrate, K3[Fe(C204)3] 3H2O, and analyze it for oxalate ion and iron. 

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