A dibenz[a,c]phenazine-Supported N-heterocyclic Carbene and Its Rhodium and Iridium Complexes

Abstract A new polycyclic N -heterocyclic carbene featuring a fused dibenz[ a , c ]phenazine moiety was generated in situ from the corresponding tetrafluoroborate salt. The synthesis and NMR data of its corresponding precursors, its sulfur adduct and dimer are reported. Complexes of type [MCl(COD)( 1 )] and [MCl(CO) 2 ( 1 )] (M = Rh and Ir, 1  = 1,3-dibutyldibenzo[ a , c ]phenazino[11,12- d ]imidazol-2-ylidene) were prepared and characterized using spectroscopic and crystallographic methods. The electron-releasing capacity of this new carbene was investigated by evaluation of its corresponding IrCl(COD) and IrCl(CO) 2 complexes by IR spectroscopy ( ν av ) and cyclic voltammetry ( E 1/2 ). These studies revealed that the electron donicity of this ligand is comparable to that of the previously reported naphthoquinone-annulated imidazolin-2-ylidene. Some preliminary studies of the photophysical properties and catalytic activity of these metal complexes are reported.