Cupferrates

In chelation complexes (sometimes called inner complexes when uncharged) the central metal ion coordinates with a polyfunctional organic base to form a stable ring compound, e.g. copper(II) acetylacetonate or iron(III) cupferrate ... 

Cupferron (ammonium salt of N-nitroso-A -phenylhydroxylamine). The reagent is used in cold aqueous solution (about 6 per cent). Metal cupferrates are soluble in diethyl ether and in chloroform, and so the reagent finds wide application in solvent-extraction separation schemes. Thus Fe(III), Ti, and Cu may be extracted from 1.2 M HC1 solution by chloroform numerous other elements may be extracted largely in acidic solution. 

Example 2 Iron (III) cupferrate gives rise to a stable ring compounds as shown below ... 

The combined GHCls extracts are washed with 20 ml of HsO to which has been added 1 ml of cupferron reagent and sufficient (NEiJeCOe soln. to make the pH 8.0-8.5. Then the Th234 Is back-extracted Into 10 ml of 3 M nitric acid containing a few ml of saturated Br2 water which serves to decompose the UXi cupferrate. This allows extraction of all the organic material and excess bromine Into the CHCle phase. 

A-Nitroso-W-phenylhydroxylamine is used as its ammonium salt (cupferron) for many extractive separations. The equilibria involved in chloroform extractions have been considered by Furman, Mason, and Pekola, who summarized in detail the properties of metaUic cupferrates. Conditions for the extraction of several metals are listed in various places. ... 

In strongly acidic media, cupferron, the ammonium salt of N-nitroso-N-phenylhy-droxylamine, seems to form with TcOf adduct [(Cupf) (Tc04)"[ or an adduct with pertechnetic acid, which can be extracted from 6 M HCl into ether by 99 %. The occurrence of any significant reduction was not observed. Tc(IIl), prepared by coulometric reduction of pertechnetate, was extracted as a cupferrate into ether up to 26% [152],... 

Wash down the sides of the two filter papers into the roundbottom flask with as little chloroform as possible to remove traces of red-brown iron-cupferrate. Distill off the chloroform until about 20 ml is left and remove the remainder of chloroform by gentle blowing or suction, as shown in Fig. 59. 

Prleser and Morrison indicate that the cupferron-lead complex can be extracted at pH 3 (Pl) The solvent is probably ieoamyl alcohol. Details of the extraction are not given but some useful separations appear possible. Figure 21 shows the pH at which the cupferrates of a number of elements can be extracted. 

C24H20CI2O4W, trans-Dichlorotetraphenoxytungsten(VI), 41B, 1126 C24H2oCl404Ti2, Dichlorodiphenoxytitanium(IV), 31B, 445 C24H2oN80eZr, Zirconium cupferrate, 35B, 748... 

Systems of the form Rh(L-L -BID)(CO)(YR3)2 that contained a five-membered monochatged bidentate ligand of the type L-L -BID (L,L -BID = monochatged bidentate ligand with donor atoms L,L variations of oxygen, nitrogen, and sulfur), such as cupferrate or tropolonate and derivatives, showed a tendency to accommodate an additional phosphine/arsine ligand (YR3, Y = P, As). ... 

Trlpoaltlve uranium. Evidence has been reported for uranlum(lll) cupferrate and uranlum(lil) chloro complexes. 

B as borate or fludborate, Al, P, Cr, Mn> Nl, Zn, and U(VI). Precipitation Is usually made In a sulfuric acid medium but hydrochloric or organic acids may be used. Nitric acid should be avoided also perchloric add If the precipitate Is to be Ignited. The presence of a reducing agent, hydrcx-ylamlne or sodium hydrosulflte, facilitates complete precipitation of uranium (IV). The cupferrate may be filtered or extracted with an organic solvent such as chlorofom. 

The properties of other metal cupferrates have been reviewed by Furman, Hason, and Pekola. ... 

Aqueous jAiase - lonlo strength = O.IM with NaOH, BClOj and NaC10j, . Na cupferrate added t O.OIJI, for Th, Sm, and La, O.OQ5M. 

A double cupfexTon separation of uranium using extraction has been adapted to the micro level. Uranlum(Vl) does not extract In the first stage, which removes many potentially Interfering elements. Ih anlumCiV), obtained In the residual aqueous solution. by reduction at a mercury cathode. Is simultaneously extracted as the cupferrate Into ether, from which It can be re-extracted Into... 

Eactraotlon and Measurement at Microgram Urahlum Level. A solution of uranium-233 (10 to 10 gram) together with about 20 y of natural iiranlum (as sulfate) was submitted to reductive extraction with cupferron for about 50 to 66 minutes. The uranium (IV/III) cupferrate was then re-extracted In cell D from the ether solution Into three suooesslve 15-ml. portions of 7H... 

Note 1. In some runs the current dropped to a low level soon after the requisite number of coulomibs had passed for about a 3-electron reduction of the uranium present. In other oases, the current did not decrease, but discontinuance of the run beyond any point where twice the theoretical current had pabsed gave satisfactory uranium recovery. In the latter oases, a gray ether-insoluble, but alcohol-soluble precipitate (apparently a mercury cupferrate), was usually evident in the aiiueous phase. The current efficiency for the desired process appeared to be good In most runs. 

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