Cobalt complexes conformation

A ligand which links the cobalt complexes with those of chromium and iron is the scorpiand diammac in its isomeric trans and cis conformations (see Scheme 5). 

Cycloalkenes, into if-allyl palladium complexes, 8, 363 Cycloalkenyl rings, metal complex conformational interconversions, 1, 414 Cycloalkynes, in nickel complexes, 8, 147 (Cyclobutadiene)cyclopentadienyl complexes, with cobalt, polymercuration, 2, 435 Cyclobutadienes... 

For cobalt(III) compounds, P. Comba calculated five of the six conformations possible for sarcophaginate complexes (Fig. 3), using strain energy minimization [230]. The sixth Dsleh conformation does not exist in cobalt(III) cages. Some structural parameters of the strain energy-minimized structures of the cobalt (III) complex conformers are presented in Table 4. 

Outer-sphere complexes of lasalocid A (LAS) anion with [Co(NH3)6], [Co(en)3], and [Co(sep)] + cations were isolated as reported in Ref 321. The X-ray data for these complexes demonstrated that three lasalocid anions (in cyclic conformation) surround the cobalt complexes so that the overall shape is approximately spherical. In consequence of its hydrophobic outer surface, the adduct is soluble in nonpolar solvents such as chloroform. Lasalocid anion was showed to act as an ionophore for selective enantiomeric transport of the [Co(sep)]- + cation through a chloroform membrane. 

At this point, the ligand is a cyclidene. Several crystal structures have shown that the conformations of the 16-membered cyclidene rings, in their complexes, are saddle shaped. This facilitates the fifth reaction, the bridging process. Since the presence of the metal ion is required to produce this saddle conformation, the process is indeed a template reaction. The lacunar ligand is then removed from the nickel(II) ion (sixth reaction) and used to form a cobalt or iron complex (last reaction). The procedures for forming the iron and cobalt complexes are different the scheme exemplifies the reactions used to synthesize the iron(II) complex. 

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