Synthesis of the cyclopentadienone rhodium complexes and investigation of their catalytic activity in the reductive amination of aldehydes in the presence of carbon monoxide

Redox-Switchable Complexes Based on Nanographene-NHCs

A series of rhodium and iridium complexes with a N‐heterocyclic carbene (NHC) ligand decorated with a perylene‐diimide‐pyrene moiety are described. Electrochemical studies reveal that the complexes can undergo two successive one‐electron reduction events, associated to the reduction of the PDI moiety attached to the NHC ligand. The reduction of the ligand produces a significant increase on its electron‐donating character, as observed from the infrared spectroelectrochemical studies. The rhodium complex was tested in the [3+2] cycloaddition of diphenylcyclopropenone and methylphenylacetylene, where it displayed a redox‐switchable behavior. The neutral complex showed moderate activity, which was suppressed when the catalyst was reduced.

Photodissociation of the Product from a Transition-Metal Center Allows the Catalytic Cycle to Proceed: The Rhodium(I)-Catalyzed [2+2+1] Carbonylative Cycloaddition of Diynes

We describe the effective rhodium(I)-catalyzed [2+2+1] carbonylative cycloaddition of diynes, yielding cyclopentadienes (CPDs), under photoirradiation. The catalysis involves the promotion of the photodissociation of the product CPD, with the simultaneous production of an essential vacant coordination site on the rhodium for an unreacted substrate. The combined use of cationic [Rh(cod)₂]BF₄ as a catalyst and photoirradiation was also found to give various CPDs in high yields (≤96%).