Well-Defined Ir/Pd Complexes with a Triazolyl-diylidene Bridge as Catalysts for Multiple Tandem Reactions

The ligand 1,2,4-trimethyl-triazolyl-diylidene has been used for the preparation of a series of three iridium/palladium heterometallic complexes that have been fully characterized. The presence of the two different metals allows tandem processes to be designed by combining reactions that are typically catalyzed by Ir and Pd. Three tandem reactions have been studied: dehalogenation/transfer hydrogenation of haloacetophenones, Suzuki-coupling/transfer hydrogenation of p-bromoacetophenone, and Suzuki-coupling/alpha-alkylation of p-bromoacetophenone. All three reactions yielded excellent outcomes to the corresponding final products, with the relevant feature that the heterodimetallic complexes are more active than the sum of the corresponding homodimetallic species. All three catalytic reactions reported here constitute unprecedented examples of tandem approaches to complex organic molecules.