Imidazolium salts imino

In order to prevent enamination, different strategies can be employed. The easiest way is to eliminate the extra CH unit that causes enamination in the first place. To this effect, imino functionalised imidazolium salts were developed that have the imino functionality directly attached to the imidazole ring of the NHC unit (see Figure 3.37). 

Figure 3.50 Synthesis of a chiral amino functionalised NHC ligand by reduction of a chiral imino functionalised imidazolium salt using NaBH. ...

Sun et al. introduced another functionality, an imino group, into the linker unit [68], The resulting phenoxyimino functionalised imidazolium salt is a potential tridentate ligand. Synthesis of the ligand starts with the corresponding salicylaldehyde and a... 

Several examples of imino-functionalized carbene complexes of palladium have been described. " The imidazolium salt 97 was prepared and coordinated to Pd by an Ag-transfer reaction. Tautomerization of the carbene-imine bond occurs during the transfer reaction to give the the enamine complex 98. Neutral and cationic Pd complexes of a second closely related chelating iminocarbene ligand, 99, were also prepared via an Ag-transfer route. " In this case, no tautomerization was reported. However, evidence of solvent-dependent hemilability was observed. 

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