Ionic ligand optimization

Ligand optimization studies for hydroformylation in ionic liquids... 

For comparison, let us also consider the ten-electron M(ligand)+ complexes for M+ = Au+ as a prototype one-pair-acceptor species. (For convenience, we refer to these species as formal Au+ complexes, but it should be understood that the actual bonding is far more covalent than the ionic label Au+ might seem to suggest.) Optimized structures for the AuL2+ complexes are shown in Fig. 4.87 for direct comparison with the Ir+ complexes in Fig. 4.86. Similarly, the energetic, geometrical, and NBO descriptors of these Au+ complexes are summarized in... 

By studying a series of complexes, it is possible to observe the differences in structural type that occur with change of cation radius. Table 6 shows the ionic radii for the alkali and alkaline earth metal cations, together with the average ligand cavity radii for simple polyethers.33 From this information it can be seen that the predicted optimal fit situation for 1 1 complexes would arise for Li+ and 12-crown-4 (74) for Na+ and 15-crown-5 (75) and for K+ and Ba2+ and 18-crown-6 (76). For 24-crown-8 (77) all of the cations have smaller radii than that of the ligating cavity. 

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