Ligand design criteria

Since no special ligand design is usually required to dissolve transition metal complexes in ionic liquids, the application of ionic ligands can be an extremely useful tool with which to immobilize the catalyst in the ionic medium. In applications in which the ionic catalyst layer is intensively extracted with a non-miscible solvent (i.e., under the conditions of biphasic catalysis or during product recovery by extraction) it is important to ensure that the amount of catalyst washed from the ionic liquid is extremely low. Full immobilization of the (often quite expensive) transition metal catalyst, combined with the possibility of recycling it, is usually a crucial criterion for the large-scale use of homogeneous catalysis (for more details see Section 5.3.5). 

One possible criterion for designating a compound complex , that the ligand is exclusively held by one metal, is too restrictive because it excludes the / -complexes. However, it is reasonable to state that if all anions contact more than three cations the solid does not contain complexed cations. Compounds made by addition of ligands to M(I)... 

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