Complexes with Optical Activity Due to Unidentate Ligands

3 Complexes with Optical Activity Due to Unidentate Ligands 

Most CD spectra have been studied to investigate various sources of optical activity such as distribution of chelate rings, conformation of chelate rings, vicinal effect due to asymmetric carbon in an optically active ligand and vicinal effect due to an asymmetric donor atom Much less studies have been done on complexes whose optical activity results from the arrangement of unidentate li nds b au such chiral complexes could not be synthesized. 

Syntheses of cw,m-[Co(CN)2(C03)(NH3)2] and w,cHCo(N02)2(C03)(NH3)2]+ are described as examples. The action of KCN on the green solution of [ 0(003)3] at room temperature gives a deep red solution containing c -[Co(CN)2(C03)2p as the main product. After neutralization with aqueous HCIO4, ammonium j r-chlorate and concentrated aqueous NH3 are mixed to the solution. After some time at a mild temperature, the concentrated solution is subjected to ion-exchange chromatography (Dowex 1-X8 in Cl form, 0.3 mol/dm NaCl eluent) to collect the desir complex species in a fraction of yellow-orange, from which cis,cis-Na[Co(CN)2(C03)(NH3)2] 2 HjO is obtained. 

Another complex, ciy,cis-[Co(N02)2(C03)(NH3)2] , was prepared from a mixture of ci5-K[Go(C03)2(NH3)2] H2O and KNO2 in water with dil. acetic acid at room temperature. After ion-exchange chromatography (Dowex 1-X8 in Cl form, 

The optical resolution of each complex synthesized was achieved by using either (—)589[Co(N02)2(en)2l C2H3O2) or (—)58g[Co(ox)(en)2 (C2H302) in an amount equivalent to half the amount of the racemate of the complex. 

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