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 L2ClM
fragments (M = Rh, Ir; L2 = 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.