A New Mixed Amino-Amido N-Heterocyclic Carbene Based on Anthranilic Acid

The synthesis of a new mixed amino-amido N-heterocyclic carbene (type A) starting from anthranilic acid is presented. A new straightforward synthetic approach to related diaminocarbenes of type B is also described. Both NHCs react with group 6 elements to form heteroureas and coordinate to L2CIM fragments (M = Rh, Ir; L-2 = COD, (CO)(2)). IR spectroscopic analysis of the carbonyl complexes reveals that the diamino-NHC is a better donor ligand (TEP: 2054 cm(-1)) compared to the amino-amido NHC (TEP: 2060 cm(-1)). In line with this behavior, a carbene dimerization to give the corresponding olefin is observed only for derivatives of type A. X-ray structure determinations are reported for two Rh complexes of ligand A and its cationic precursor.