Cobalt partial resolution

Cr(acac)3] and enriched samples of (- -)-[Ru(acac)3] have been isolated by treatment of aqueous solutions of the corresponding (-l-)-tartrate complexes with Hacac at high pH followed by recrystalUzation of the partially resolved mixture. Partial resolution of the tris(acetylacetonates) of Cr, Co, Ru and Rh, and also the cis and trans isomers of cobalt benzoylacetonate have been achieved by column chromatography on D-(- -)-lactose. ... 

The active C(j-bromoamminebis(ethylenediamine)cobalt(III) salts, like the racemic compounds, are similar in properties to the corresponding cis-chloroamminebis(ethylenediamine)cobalt(III) salts, but they have been less extensively investigated. They are quite stable, and their solutions do not race-mize on standing at room temperature or even on heating to incipient boil-ing.i They can be converted from one salt to another without loss of optical activity. Treatment of the active bromide or(+)-a-bromocamphor- r-sulfonate with liquid ammonia yields the corresponding optically active cw-diammine-bis(ethylenediamine)cobalt(III) salts. A partial resolution of the racemic bromide into optical isomers on ( +)- and ( — )-quartz has been reported.The specific magnetic susceptibility has been found to be 3.49 X... 

In the early belief that these reactions were completely stereospecific, we felt that the reaction of [Co(1-pn)2CI2]+ with carbonate could not give an optical inversion under any experimental conditions. This is, of course, not true, as was soon shown by the work of McReynolds (28) and Sister Mary Martinette Hagan (29). In a cobalt complex containing asymmetric ligands, one form is preferred, but both forms can and do exist. In the same belief, we hoped that stereospecific effects could be used in the resolution of racemic potential ligands. This does give partial resolution, as shown by the work of Johnson (30),... 

Chromatography with D(-l-)-lactose hydrate columns was used in the partial resolution of tris(acetylacetonato)cobalt II) complex partial resolution of [Co(acac)3], and mer- and c-[Co(bzac)3] (bzac = benzoylacetonate) is also effected by column chromatography on (H-)-lactos . The [Co(bzac)3] complex prepared from Na3[Co(C03)3] 3 H2O was separated into its mer and fac geometrical isomers by column chromatography on Florisil (Florodin Co., suj rior to alumina), prior to the resolution. For the resolution, (-l-)-lactose dried at 110 °C and then sieved to 100 mesh, and a chromatographic column (3.9 x 230 cm), which narrowed to 3.0 cm at... 

In these syntheses, Peppard had to rely on the very weak trans effect in the cobalt complex [Co(NH3) i (SO3) 2 ]-. The cis-dichloro-cis-diammineethylenediaminecobalt(III) ion is asymmetric, and Peppard partially resolved it into its enantiomeric forms by adsorption on quartz ground to 100 mesh. This method of resolution is frequently, but not always, effective. Before it can be fully utilized, we will need to learn a great deal more about the principles of adsorption. The preparation of Peppard s isomer s is particularly interesting because cobalt(III) complexes rearrange easily, whereas the platinum compounds do not. 

In 1966, [Co(en)3] Bfj was separated into its optically active enantiomers on a colunm of anion-exchange resin, which was in advance loaded with tartrate or anti-monyltartrate ions. The resolution was partial. In the same year, Brubaker et al. achieved the total resolution of a trinuclear cobalt(III) complex, hexakis(2-amino-ethanethiolato)tricobalt(III) bromide on a column of a cation-exchange cellulose (Bio-Rad Cellex CM) by eluting with 0.1 mol/dm NaCl. 

Apoenzyme may be prepared from E. coli cells grown in the absence of added B12 compounds. Instability of the protein in this form has limited purification, but a partially purified preparation has been obtained (Weissbach et al., 1963) and, very recently, a means of chemical resolution of purified holoenzyme has been reported (Taylor, 1970). The apoenzyme is readily converted to holoenzyme by incubation with methyl-Bii in the absence of a reducing system (Guest et al., 1962 Weissbach et al., 1965). Ethyl-Bi2 and -propionate-Bi2 are also active. For cobalamins which possess no carbon-cobalt bond to react with apoenzyme to form holoenzyme a reducing system is required (Guest et al., 1960, 1962 Takeyama and Buchanan, 1961 Takeyama et al., 1961 ... 

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