Donor-functionalized imidazolium salts

Alternatively, complexes 54 and 55 with abnormally bound NHC ligands have been obtained by oxidative addition of a C-H bond to Pd° and Pt° while blocking the C2 position of the azolium salt [155] or even without any blocking of the C2 position by oxidative addition of a C5-I bond of a donor-functionalized imidazolium cation (Fig. 19) [156]. 

A large number of differently bridged diazolium salts of type 24 (Figure 1.4) have been described. Compound 25, the precursor for an interesting bis-carbene containing carbene and alcoholato donor functions, was prepared by Arnold et al. by the reaction of two equivalents of an A-alkylimidazole with a functionalized epichlorhydrin (Figure 1.4). Dibenzimidazolium salts are also known. Trisimidazolium salt 26 was first described by Dias and Jin, " shortly thereafter followed by the description of trisimidazolium salts of type 27. Tripodal tris-imidazolium salts of types 26, 28 and 29 were prepared by Hu and Meyer. ... 

Macrocyclic bis(imidazolium) salt 56" possesses after C2 deprotonation both NHC and pyridine donor functions. The doubly lutidine-bridged... 

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