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Catalyst Deactivation of a Monoligated CyJohnPhos-bound Nickel(0) Complex
Samuel H Newman-Stonebraker1,2, T Judah Raab2, Abigail G Doyle2
1Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA.
Nickel(0) catalysts can deactivate through dimerization after the catalytic cycle. Intercepting the active nickel(0) species with substrates or ligands prevents this irreversible catalyst deactivation.
Area of Science:
- Organometallic Chemistry
- Catalysis
- Synthetic Chemistry
Background:
- Cross-coupling catalysts are essential in synthetic chemistry but suffer from side reactions.
- Understanding catalyst deactivation pathways is crucial for optimizing reactions and designing new catalysts.
Purpose of the Study:
- To investigate the off-cycle reactivity of a monoligated nickel(0) complex with CyJohnPhos ligand.
- To elucidate the dimerization and C-P bond activation pathways leading to catalyst deactivation.
Main Methods:
- Structural characterization of nickel(0)/nickel(0) and nickel(0)/nickel(II) dimers.
- Investigation of nickel(0) complex reactivity in the absence of substrates and additives.
Main Results:
- A monoligated CyJohnPhos-bound Ni(0) complex undergoes dimerization after reductive elimination.
- C-P bond activation of the phosphine ligand forms a phosphido-bridged Ni(0)/Ni(II) dimer.
- Monomeric Ni(0) species must be intercepted by substrate or ligand to prevent deactivation.
Conclusions:
- Dimerization and C-P bond activation represent significant off-cycle deactivation pathways for this nickel catalyst.
- Ligand and substrate coordination are essential to maintain the active monomeric Ni(0) species.
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