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Secondary Coordination Sphere Alkylation Promotes Cyclometalation
Joseph A Zurakowski1, Kasey R Brown1, Marcus W Drover1
1Department of Chemistry and Biochemistry, The University of Windsor, 401 Sunset Avenue, Windsor, Ontario N9B 3P4, Canada.
Inorganic Chemistry
|April 30, 2023
Summary
Researchers installed a Lewis-acidic secondary coordination sphere onto diphosphine ligands in iron complexes. This modification enabled facile cyclometalation at iron, a key transformation in organometallic chemistry.
Area of Science:
- Organometallic Chemistry
- Coordination Chemistry
- Ligand Design
Background:
- Diphosphine ligands are crucial in transition-metal chemistry, influencing reactivity and stability.
- Secondary coordination spheres (SCS) can modulate the electronic and steric properties of metal complexes.
- Cyclometalation is a fundamental reaction pathway in organometallic chemistry.
Purpose of the Study:
- To synthesize and characterize novel iron complexes featuring a Lewis-acidic SCS on diphosphine ligands.
- To investigate the impact of SCS incorporation on the reactivity of iron complexes, specifically towards cyclometalation.
- To compare the reactivity of modified diphosphine ligands with their unmodified counterparts.
Main Methods:
- Synthesis of iron complexes with 1,2-bis(di-allylphosphino)ethane (tape) ligand.
- Installation of a Lewis-acidic SCS via allyl group hydroboration using dicyclohexylborane.
- Reaction of the modified iron complex with n-butyllithium to induce cyclometalation.
Main Results:
- Successful synthesis of the chloride complex [Cp*Fe(P2B^Cy4)(Cl)] featuring the modified diphosphine ligand.
- Observation of facile cyclometalation at iron upon treatment with n-butyllithium.
- Contrast in reactivity compared to iron complexes with unmodified diphosphine ligands (e.g., dnppe).
Conclusions:
- Lewis acid SCS incorporation onto diphosphine ligands is an effective strategy to promote cyclometalation.
- The electronic and steric effects of the SCS significantly influence the reactivity of iron complexes.
- This work provides a new route to access cyclometalated iron species through ligand modification.
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