A dibenz[a,c]phenazine-supported N-heterocyclic carbene and its rhodium and iridium complexes

•A dibenz[a,c]phenazine-fused imidazol-2-ylidene was generated in situ.•The carbene donicity is reduced as result of fusion with the polycyclic moiety.•A series of metal complexes were synthesized and structurally characterized.•The imidazolium salt precursor and the metal complexes are fluorescent.•The catalytic activities of the metal complexes were evaluated in hydrosilylation reaction.

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 (νav) and cyclic voltammetry (E1/2). 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.

Graphical abstractA new polycyclic N-heterocyclic carbene featuring a fused dibenz[a,c]phenazine moiety was generated in situ. Complexes of type [MCl(COD)] and [MCl(CO)2] (M = Rh and Ir) incorporating this carbene were prepared and characterized using spectroscopic and crystallographic methods. These metal complexes show excellent catalytic activity in hydrosilylation of acetophenone derivatives.Figure optionsDownload full-size imageDownload as PowerPoint slide