Metal Complexes of Very Bulky N,N′-Diarylimidazolylidene N-Heterocyclic Carbene (NHC) Ligands with 2,4,6-Cycloalkyl Substituents

1,3,5-Tricycloalkylbenzene (cycloalkyl = C5H9, C6H11) was converted into the respective anilines (by means of nitration and reduction) and then into the corresponding diimines (with glyoxal), the cyclization of which with (HCHO)(n)/ZnCl2 provided the respective 1,3-bis(2,4,6-tricyclopentylphenyl)imidazolium salt in modest yields. An analogous reaction sequence that employed acenaphthene-1,2-dione instead of glyoxal yielded the two azolium salts in good yields, which were converted into the respective N-heterocyclic carbene (NHC) complexes [(NHC)AgCl], [(NHC)AuCl], [(NHC)RhCl(cod)] (cod = cyclooctadiene), and [(NHC)RhCl(CO)(2)].