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Ir III /Au I and Rh III /Au I Heterobimetallic Complexes as Catalysts for the Coupling of Nitrobenzene and Benzylic Alcohol

2018; American Chemical Society; Volume: 37; Issue: 21 Linguagem: Inglês

10.1021/acs.organomet.8b00642

1520-6041

Maximilian Böhmer, Florian Kampert, Tristan Tsai Yuan Tan, Gregorio Guisado‐Barrios, Eduardo Peris, F. Ekkehardt Hahn,

Synthetic Organic Chemistry Methods

Two simple bisimidazolium salts derived from m- or p-bisimidazolebenzenes have been used as ligand precursors for the preparation of a series of heterobimetallic RhIII/AuI and IrIII/AuI complexes. All complexes have been fully characterized, and the molecular structures of selected derivatives have been determined by X-ray diffraction studies. These analyses showed that, regardless of the ligand used, the direct coordination environment of the metals is composed of identical donors (MIII: CNHC, Cbenzene, η5-Cp*, and I–; AuI: CNHC and I–) and is rather similar in the heterobimetallic complexes. The catalytic activity of the heterobimetallic complexes in the coupling of nitrobenzene with benzylic alcohol has been investigated. In all cases, the performance observed for the heterobimetallic complexes was superior to that shown by mixtures of homometallic MIII/AuI complexes, suggesting a cooperative effect between the two metal centers. In addition and in spite of the similarity of the donor groups of the two bis-NHC ligands used, the slightly different relative orientation of the two metals in the heterobimetallic complexes also plays a role in the catalytic conversion observed.