Amino Group Functionalized N‑Heterocyclic 1,2,4-Triazole-Derived Carbenes: Structural Diversity of Rhodium(I) Complexes

The synthesis of the amino group
functionalized NHC precursor 1-tert-butyl-4-(2-((dimethylamino)­methyl)-phenyl)-3-phenyl-4H-1,2,4-triazol-1-ium perchlorate has been developed. The
generation and bonding properties of the NHC ligand have been evaluated
in reactions toward three Rh­(I) complexes[Rh­(COD)­Cl]2, [Rh­(cyclooctene)2Cl]2, and [Rh­(ethylene)2Cl]2, respectively. For the first complex, [(NHC)­RhCl­(COD)],
the coordination of the dangling amino group was not observed because
of the fully occupied coordination neighborhood of the Rh atom. On
the other hand, in the case of [(NHC)­RhCl­(ethylene)], [(NHC)­RhCl­(cyclooctene)],
[(NHC)­Rh­(COD)]+[BF4]−, and
[(NHC)­RhCl­(CO)] a strong intramolecular coordination of the amino
nitrogen atom was revealed, thus forming the unusual seven-membered
diazametallacycle. All of the products of these reactions were characterized
in solution by NMR spectroscopy as well as in the solid state by X-ray
diffraction analysis.