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Rhodium(I) complexes with proton-responsive anionic tethered N-heterocyclic carbene ligands: synthesis and
Mert Olgun Karataş1,2, Diego R Hinojosa1, Vincenzo Passarelli1
1Instituto de Síntesis Química y Catálisis Homogénea (ISQCH)-Departamento de Química Inorgánica, CSIC-Universidad de Zaragoza, C/Pedro Cerbuna 12, CP. 50009, Zaragoza, Spain. mkaratas@unizar.es.
This study introduces novel rhodium(I) complexes with anionic-tethered N-heterocyclic carbene ligands for alkyne homocoupling. N-based ligands show catalytic activity, unlike carboxylato counterparts, with distinct mechanisms influencing selectivity.
Area of Science:
- Organometallic Chemistry
- Catalysis
- Coordination Chemistry
Background:
- N-heterocyclic carbenes (NHCs) are versatile ligands in organometallic chemistry.
- Rhodium complexes are widely used as catalysts in organic transformations.
- Tethered ligands offer unique coordination modes and influence catalytic activity.
Purpose of the Study:
- To synthesize novel rhodium(I) complexes featuring anionic-tethered NHC ligands.
- To investigate the application of these complexes in alkyne homocoupling reactions.
- To explore the structure-activity relationship and mechanistic aspects of the catalysis.
Main Methods:
- Synthesis and characterization of rhodium(I) complexes with pyridonato, amidato, and carboxylato-functionalized NHC ligands.
- Investigation of catalytic activity in alkyne homocoupling reactions.
- Mechanistic studies involving protonation, alkyne insertion, and selectivity determination.
Main Results:
- Successfully prepared rhodium(I) complexes forming 5, 6, and 7-membered metallacycles.
- Demonstrated catalytic activity for alkyne dimerization with N-based anionic ligands (pyridonato, amidato).
- Observed distinct catalytic mechanisms (proton transfer vs. alkyne insertion) influencing selectivity based on ligand type and co-ligands.
Conclusions:
- Anionic-tethered NHC ligands provide tunable coordination environments for rhodium catalysis.
- The nature of the anionic tether significantly impacts catalytic performance and mechanism in alkyne homocoupling.
- This work expands the scope of NHC-ligated rhodium catalysts for C-C bond formation.
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