Rollover Cyclometalation as a Valuable Tool for Regioselective C–H Bond Activation and Functionalization

Rollover cyclometalation constitutes a particular case of cyclometallation reaction. This reaction occurs when a chelated heterocyclic ligand loses its bidentate coordination mode and undergoes an internal rotation, after which a remote C–H bond is regioselectively activated, affording an uncommon cyclometalated complex, called “rollover cyclometalated complex”. The key of the process is the internal rotation of the ligand, which occurs before the C−H bond activation and releases from coordination a donor atom. The new “rollover” ligand has peculiar properties, being a ligand with multiple personalities, no more a spectator in the reactivity of the complex. The main reason of this peculiarity is the presence of an uncoordinated donor atom (the one initially involved in the chelation), able to promote a series of reactions not available for classic cyclometalated complexes. The rollover reaction is highly regioselective, because the activated C–H bond is usually in a symmetric position with respect to the donor atom which detaches from the metal stating the rollover process. Due to this novel behavior, a series of potential applications have appeared in the literature, in fields such as catalysis, organic synthesis, and advanced materials.

Exploration of the Structural and Photophysical Characteristics of Mono- and Binuclear Ir(III) Cyclometalated Complexes for Optoelectronic Applications

Intrinsic characteristics possessed and exhibited by Ir(III) cyclometalated complexes need to be further examined, understood, and explored for greater value enhancement and potentiation. This work focuses primarily on the comparative studies of the ligand structures, types, and their substituent influence on the photophysical and optoelectronic properties of typical cyclometalated mono- and binuclear iridium(III) complexes in solution or solid states.

New Pt→M (M = Ag or Tl) complexes based on anionic cyclometalated Pt(ii) complexes

Anionic cyclometalated complexes (NBu4)[Pt(CNC)X] (X = Cl, CN, or S-2py) react with Ag(i) and Tl(i) salts to give complexes containing Pt→M donor–acceptor intermetallic bonds. These complexes show a wide range of structural dispositions depending on M and the bridging characteristics of the ligand X.

Two platinum(ii) complexes with a 4-phenyl-4H-1,2,4-triazole derivative as an ancillary ligand for efficient green OLEDs

Two efficient green platinum(ii) cyclometalated complexes were applied in organic light-emitting diodes showing good performances with a peak current efficiency of 88.50 cd A−1 and a peak external quantum efficiency of 26.90% with mild efficiency roll-off.