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Uranium Metallocene Azides, Isocyanates, and Their Borane-Capped Lewis Adducts
Michael A Boreen1,2, Karl N McCabe3, Trevor D Lohrey1,2
1Department of Chemistry, University of California, Berkeley, California 94720, United States.
Inorganic Chemistry
|May 29, 2020
Summary
New uranium complexes with bulky ligands were synthesized, featuring azide and cyanate ligands. Differences in their electronic properties and reactivity were observed, providing insights into uranium-ligand bonding. Computational analysis further elucidated these interactions.
Area of Science:
- Organometallic Chemistry
- Uranium Chemistry
- Coordination Chemistry
Background:
- Uranium metallocene complexes are of interest for their unique electronic and structural properties.
- The bulky tetra(isopropyl)cyclopentadienyl (CpiPr4) ligand influences the coordination environment and reactivity of uranium centers.
Purpose of the Study:
- To synthesize and characterize novel uranium(IV) and uranium(III) complexes with azide and cyanate ligands.
- To investigate the structural, electronic, and reactivity differences between related azide and cyanate complexes.
- To explore the coordination behavior of borane Lewis acids with uranium-azide and uranium-cyanate systems.
Main Methods:
- Synthesis of uranium metallocene complexes via reactions with pseudohalide salts.
- Isolation and characterization of mixed-ligand and borane-capped complexes.
- X-ray crystallography for structural determination.
- Cyclic voltammetry and UV-vis spectroscopy for electronic property analysis.
- Computational analysis (DFT) to understand bonding and energetics.
Main Results:
- Successfully synthesized uranium(IV) complexes (CpiPr4)2U(N3)2, (CpiPr4)2U(NCO)2, and a mixed-ligand species.
- Characterized borane-capped complexes (CpiPr4)2U(N3)[(μ-η1:η1-N3)B(C6F5)3] and (CpiPr4)2U(NCO)[(μ-η1:η1-OCN)B(C6F5)3].
- Isolated a uranium(III) cyanate-bridged molecular square [(CpiPr4)2U(μ-η1:η1-OCN)]4.
- Observed subtle electronic differences and nearly identical solid-state structures between azide and cyanate complexes.
- Demonstrated significant reactivity differences between uranium(III) cyanate and azide complexes.
Conclusions:
- The bulky CpiPr4 ligand facilitates the synthesis of diverse uranium metallocene complexes.
- Borane coordination to azide and cyanate ligands leads to distinct structural arrangements and influences bonding.
- Uranium(III) cyanates and azides exhibit markedly different chemical behaviors.
- Computational studies provide a framework for understanding linkage isomer preferences and bonding interactions in these uranium complexes.
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