Cations, with ethylenediamine trans

The procedure described here is based on the observation that amine monohydroxo complexes of cobalt(III), rhodium(IIl), and iridium(III) react directly with carbon dioxide to form the corresponding carbonato complexes,2 3 without effect on the configuration of the amine ligands.4 The amine monoaqua complex is allowed to react with lithium carbonate or carbon dioxide gas at room temperature at pH 8.0 for a few minutes, and the carbonato complex is isolated by adding alcohol. The procedure has been used to prepare salts of the following cations pentaammine(carbonato)-cobalt(III),2 ds-ammine(carbonato)bis(ethylenediamine)cobalt(III),5 trans-... 

It was mentioned above that tris(chelate) complexes of the type [Colenlj] lack an improper axis of rotation. As a result, such complexes can exist in either of two enantiomeric forms (or a racemic mixture of the two). Figure 12.20 illustrates the complex ions [ 0(00)3] and [Crioxlj] ", each of which is chiral with Dj symmetry. It is not necessary to have three chelate rings present. The cation dichloro-bis(ethylenediamine)cobaIt(III) exists as two geometric isomers, cis and trans. The trans isomer has approximate Dj, symmetry (Fig. 12.21b). Because it has three internal mirror planes, it is achiral. The cis isomer has C, symmetry and is chiral (Fig. 12.2la). Since the two chloride ions replace two nitrogen atoms from an eth-... 

Fedin and coworkers [102,103] have isolated a number of distinct species within CB[n] nanoreactors. For example, they identified a previously unrecognized hydronium di-cation in a solid-state complex with CB[6] [102]. Instead of the commonly recognized H7 O3 monocation (essentially a proton coordinated by three water molecules), they observed a cyclic H14 OJ species, stabilized and templated by a set of five hydrogen bonds to the CB[6] portal carbonyls, forming an exclusion complex. In another report, they showed that the trans form of the metal complex [Co(en)2Cl2r (en = ethylenediamine) was selectively encapsulated in CB[8] from a mixture of cis and trans complexes [103]. Furthermore, the trans complex was thermally stabilized in the CB[8] nanoreactor. This shows the potential utility of CB[n] nanoreactors to select specific reactant isomers for subsequent selective reactions. 

A considerable amount of kinetic and mechanistic data has been reported for the base hydrolysis of cis- and trans-dihalobis(ethylenediamine)-cobalt(III) cations/ On the other hand, the only chromium(III) analogs which have been studied are cis- and trans-dichlorobis(ethylenediamine)-chromium(III) cations/ The present study was undertaken to gain additional base hydrolysis data for dihalobis(ethylenediamine)chromium(III) complexes, which will permit a more meaningful comparison with their cobalt(III) analogs. 

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