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Oxygen Atom Transfer to Cationic PCPNi(II) Complexes Using Amine-N-Oxides
Etienne A LaPierre1, Marissa L Clapson1, Warren E Piers1
1Department of Chemistry, University of Calgary , 2500 University Drive N.W., Calgary, Alberta, Canada T2N 1N4.
Inorganic Chemistry
|December 21, 2017
Summary
This study explores nickel(II) pincer complexes reacting with amine-N-oxides. The research reveals direct oxygen atom insertion into nickel-phosphine bonds, forming oxidized pincer ligands without transient nickel(IV) oxo intermediates.
Area of Science:
- Organometallic Chemistry
- Coordination Chemistry
- Catalysis Research
Background:
- Square planar Ni(II) complexes supported by PCsp3P pincer ligands were synthesized.
- Ligand variations influenced complex stability and reactivity.
- Amine-N-oxides are common oxygen atom transfer agents in coordination chemistry.
Purpose of the Study:
- To investigate the reactivity of Ni(II) pincer complexes with amine-N-oxide oxygen atom transfer agents.
- To elucidate the mechanism of ligand oxidation and oxygen atom transfer.
- To explore the potential involvement of high-valent nickel intermediates.
Main Methods:
- Synthesis and characterization of novel nickel(II) bromide, triflate, and hexafluoroantimonate complexes.
- X-ray crystallography was employed to determine the structures of key compounds.
- Reactions with different amine-N-oxides were studied, followed by DFT computations.
Main Results:
- Oxidation of one or both phosphine arms of the pincer ligand was observed upon reaction with amine-N-oxides.
- Direct oxygen atom insertion into Ni-P bonds was confirmed as the dominant pathway.
- Transient Ni(IV) oxo intermediates were not detected and are unlikely to be involved.
Conclusions:
- The study demonstrates a novel pathway for ligand functionalization in Ni(II) pincer complexes.
- Oxygen atom transfer occurs via direct insertion, bypassing high-valent nickel species.
- This work provides insights into the mechanisms of oxidation reactions relevant to catalysis.
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