Acidato complexes

Reactions of Long-Chain Acidato Complexes of Transition Metals in Micelles and Microemulsions... 

The cobalt acidato complexes are readily prepared from the pentammineaquacobalt(III) perchlorate, Cp(NIl3)5H20 (0104)3. As reported elsewhere ), the aqua complex is added to a 10-fold... 

Several years later, the preparative work on the geometrical isomers was renewed by other workers, who applied the three methods to the preparation of geometrical-optical isomers, or diastereoisomers, of tris-complexes from optically active amino acids. In general, four diastereoisomers are possible for a tris(L- or o-amino-acidato) complex fac ->r), fac —), wer(-t-) and mer —). 

Shibata et al. proposed a general procedure for the synthesis of mixed amino-acidato complexes using the green solution of tricarbonatocobaltate(III). The procedure was based on the fact that it is more difficult for a ligand to be substituted for the third carbonate li nd of [Co(C03)3f than for the first and second carbonate ligands. That is, in the first step a bis(amino-acidato)carbonatocobaltate(III) complex is produced and then the reaction with another amino acid leads to the formation of the desired mixed amino-acidato complex, e.g. 

Figure 4.1 shows the spatial distribution of the alkyl substituents, R, in the four isomers of a tris-(L-a-amino-acidato) complex [Co(l-NH2CHRCOO)3]. The substituents are arranged either in a pseudo-axial or in a pseudo-equatorial orientation to the threefold or pseudo-threefold axis of the isomers. The A isomers of both fac and mer have pseudo-equatorial substituents, while the A isomers have pseudo-axial ones. In the mer-ts. isomer, two substituents are axially disposed at one end of the pseudo-threefold axis and the third at the opposite end. In the mer-h isomer, there is an exceptionally small distance between two substituents. 

The absorption and CD spectral data for several tri L-amino-acidato) complexes are cited in Table 4.3. 

Various amino acid complexes of the general type [Co(en)2AA] (AA = amino acidate) have been reacted with thionyl chloride in DMF. Provided the amino acid side-chain does not contain functionalities that react with SOCI2, the complexes undergo facile oxidation to give the related a-imino acidato complex. A mechanism is proposed for these reactions. 

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