Cobalt complexes, nonelectrolytes

Occasionally, solubility properties are such that it is possible to apply the ideas of the less soluble diastereoisomer to diastereoisomeric nonelectrolytes. For example, among the four possible (D- and L-1,2,3, D- and L-1,2,6) tris-L-alaninato complexes of cobalt(III) and rhodium(III) one in each case is utterly insoluble in water, the others being rather soluble (149). The insoluble cobalt complex is the D(+)-l,2,3 isomer (sometimes called / , fac, or cis), and the isomorphous insoluble rhodium complex is almost certainly D(—)-l,2,3-[Rh(Lala)3],... 

The following general type of complexes has been studied extensively (Figure 5). These bidentate ligands, which form bis-complexes of nickel (II), copper(II), and cobalt(II), are nonelectrolytes and therefore have moderate solubility in nonpolar, noncoordinating solvents. Furthermore, using these solvents reduces additional coordination. The equilibrium between the planar and pseudo-tetrahedral conformations may be altered by changes in solvent, temperature, and substituents. 

J0rgensen s chain theory for some cobalt(III) complexes (top), compared with the Werner representations (bottom). Werner s representation for [CoC13(NH3)3] fits the nonelectrolyte behaviour seen experimentally, unlike the Jprgensen model. 

In 1964, Madd(x k and Todesco reported the IR spectral studio of a number of cobalt(III) complexes in their report, they concluded that the cis-cis or fac isomer of Majumdar et al. which still gave the nonelectrolyte composition, was in fact an ionisation isomer of the [Co(N02)2(NH3) ] Co(N02) (NH3)2] type. 

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