Cobalt resolving agent

Schwarzenbach3 prepared the sparingly soluble salt dZ-eis-dinitrobis (ethylenediamine) cobalt (III) ethylenedi-aminetetraacetatocobaltate(III). The present rapid method of resolution utilizes d- or Z-cis-dinitrobis (ethylenediamine) cobalt (I II) chloride as the resolving agent. 

The C2S-dinitrobis(ethylenediamine)cobalt(III) ion was first resolved by Werner1,213 through the d-camphorsulfo-nate. However, that method, though it ultimately gives good yields of both optical antipodes, is laborious, and the resolving agent is comparatively expensive. Resolution is readily accomplished by the use of potassium cZ-antimony tartrate, and yields of each antipode of the order of 40 to 50% are obtained. 

Because the optically active forms of the (ethylenediamine)bis-(oxalato)cobaltate(III) ion have been, and will continue to be, excellent resolving agents for many cationic cobalt(III) complexes, it is only proper that a detailed resolution procedure be developed to produce both enantiomorphic forms in useful quantities. 

Racemic acetylacetonatobis(ethylenediamine)cobalt(III) ion was first prepared by Werner and Matissen from the hydroxoaquo complex. Later Werner, Schwyzer, and Kar-rer prepared the optical antipodes from the resolved chloro-aquobis(ethylenediamine)cobalt(III) cation. The present method describes an efficient preparation and a simple resolution of the racemic salt using sodium (-l-)-arsenyl tartrate as the resolving agent. 

The first successful resolution of coordination compounds was reported by Werner in 1911 and involved two series of complexes, the cw-chloroammine-bis(ethylenediamine)cobalt(III) series (with V. L. King) and the m-bromo-amminebis(ethylenediamine)cobalt(III) series (with E. Scholze). Of the two, the bromoammine series is easier to resolve because of the greater difference in solubility between the diastereoisomers that are formed with the resolving agent, silver ( + )-octahedral configuration first postulated by Werner for cobalt(III) in 1893. 

The optical resolution of racemicp-hydroxypheny Iglycine with 3-bromocamphor-8-sulfonic acid has also been achieved. This resolving agent has also been widely used in the preparation of optically pure chromium and cobalt complexes. ... 

N.CoKOtCIis - 0.5H2O, Cobaltatc(III), diam-mine(carbonato)dinitro-, cis.cis-, potassium, hemihydrate, 23 70 N4CoK08C2H<, 0.5H2O, Cobaltate(lll), diam-minedinitro(oxalato)-, cis.cis-, potassium, hemihydrate, 23 71 N4Co04QH, , Cobalt(Ill), bis(l,2-ethanedi-amine)(oxalato)-, as resolving agent, 23 65... 

Werner resolved the tris oxalate using strychninium ion in 1912. Other effective resolving agents for the tris complex include (+ )-tris(l,10-phenanthroline)nickel(II), ( + )- or (- )-tris(ethylenediamine)cobalt(III) and (- )-tris(ethylenediamine)rhodium(III). The (- )-[Co(ox)3] ion has been studied by single-crystal methods and has the d configuration. It has been related to (-i-)-[Cr(ox)3] by X-ray powder photography, so its absolute configuration is also established as d by the more exact form of the rule of least-soluble diastereoisomers. ... 

The yellow compound potassium (-l-)tris-(L-cysteine-sulphinato(2 —)-SN)-cobalt(iii) is very easily prepared by a rapid stereoselective synthesis from L-cysteine, and has proved a very good resolving agent for tripositive cations. " The anions [Co(L-Pro-iV-prop)2] , [Co(L-Pro-iV-ac)(ida)], [Co-... 

The Q -bromocamphor-7r-sulfonate in the filtrate from the precipitation of the Z-as-dichloro salt can be recovered by adding an excess of ammonium carbonate and evaporating to small volume. On cooling, the ammonium salt of the resolving agent crystallizes, leaving the extremely soluble carbonatobis(ethylenediamine)cobalt(III) chloride in solution. The hydrochloric acid-alcohol-ether mixtu ... 

Extending the scope of combined chiral selector systems beyond CDs, one may note that this mode has been used in CE for a rather long time [53-56], The very first example of combined chiral selectors in CE seems to be the report by Fanali et al. [53] in 1989 when 15 mM L-(+)-tartaric acid buffer was used in combination with 15 mM P-CD in order to resolve the enantiomers of chiral cobalt complexes. CDs have also been combined with chiral surfactants such as cholic acids [54, 55] and synthetic micelle-forming agents [56], In recent years, several studies were published on the combination of CDs with chiral [57, 58] and achiral [51, 59-61] crown ethers. The latter studies [59-62] where the achiral crown ether cannot contribute to enantioseparations independently clearly illustrate that the simplified approach described in [12, 47] may not be universally applied to all dual chiral separation systems in CE. 

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