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Synthesis and structures of Co bis-trifluoromethylpyrazolate complexes
Joseph H Rivers1, Richard A Jones
1Department of Chemistry and Biochemistry, The University of Texas at Austin, Welch Hall 2.204, 105 E. 24th St. STOP A5300, Austin, Texas 78712-1224, USA. rajones@cm.utexas.edu.
Dalton Transactions (Cambridge, England : 2003)
|May 2, 2013
Summary
Researchers synthesized novel cobalt complexes with bis-trifluoromethylpyrazolate ligands. These reactions explore cobalt coordination chemistry and yield new compounds characterized by spectroscopy and X-ray diffraction.
Area of Science:
- Organometallic Chemistry
- Coordination Chemistry
- Inorganic Synthesis
Background:
- Cobalt complexes with phosphine ligands are important in catalysis.
- Pyrazolate ligands offer tunable electronic and steric properties.
- Fluorinated ligands can influence complex stability and reactivity.
Purpose of the Study:
- To synthesize and characterize new cobalt complexes featuring bis-trifluoromethylpyrazolate ligands.
- To investigate the reactivity of these complexes with oxygen and other reagents.
- To explore unusual coordination modes and oxidation states in cobalt complexes.
Main Methods:
- Reactions of cobalt precursors (CoCl2, Co(PMe3)3Cl, Co(PMe3)4) with sodium or lithium bis-trifluoromethylpyrazolate.
- Characterization using spectroscopic techniques (NMR, IR, UV-Vis).
- Single crystal X-ray diffraction for structural determination.
Main Results:
- Synthesis of cobalt complexes Co(PMe3)3(3,5-(CF3)2-Pz) (1), Co(PMe3)3(3,5-(CF3)2-Pz)2 (2), [cis-Co(PMe3)4H2][Co(PMe3)(3,5-(CF3)2-Pz)3] (3), (3,5-(CF3)2-Pz)2Co(μ-3,5-(CF3)2-Pz)(μ-OPMe3)Li(OPMe3)2 (4), [(PMe3)Co(μ-3,5-(CF3)2-Pz)2(μ(3)-OH)Li]2 (5), and Co(OPMe3)2(3,5-(CF3)2-Pz)2 (6).
- Complex 3 exhibits an unusual ion pair structure with Co(III) and Co(II) centers.
- Reactions with O2 yield oxidized products, indicating sensitivity to oxygen.
Conclusions:
- Novel cobalt complexes with bis-trifluoromethylpyrazolate ligands have been successfully synthesized.
- The study reveals diverse coordination behaviors and the formation of unusual structures.
- The reactivity of these complexes, particularly towards oxygen, provides insights into their stability and potential applications.
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