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Characterization of Co-C bonding in dichlorovinylcobaloxime complexes
Angela D Follett1, Katherine A McNabb, Alicia A Peterson
1Department of Chemistry and Supercomputing Institute, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, USA.
Inorganic Chemistry
|February 9, 2007
Summary
Cobalt dichlorovinyl complexes feature strong Co-C bonds due to high s-character, not pi-bonding. Reductive cleavage yields a dichlorovinyl anion, crucial for trichloroethylene dechlorination mechanisms.
Area of Science:
- Organometallic Chemistry
- Environmental Chemistry
- Computational Chemistry
Background:
- Cobalt complexes are key in environmental remediation, particularly in trichloroethylene dechlorination.
- Dichlorovinyl cobalt complexes act as critical intermediates in these reactions.
- Understanding Co-C bonding and cleavage is vital for optimizing remediation strategies.
Purpose of the Study:
- To investigate cobalt-carbon (Co-C) bonding and reductive Co-C cleavage in cobalt dichlorovinyl complexes.
- To elucidate the role of ligand electronics in influencing Co-C bond characteristics.
- To determine the mechanism of Co-C bond cleavage following reduction.
Main Methods:
- Synthesis and characterization of seven cis-1,2-dichlorovinyl(L)cobaloxime complexes.
- Spectroscopic analysis (1H NMR, 13C NMR) and X-ray crystallography.
- Electrochemical studies (cyclic voltammetry) and electronic structure calculations.
Main Results:
- Co-C bond length slightly increases with electron-donating pyridine ligands; C=C bond length remains consistent.
- Electronic structure calculations and metrical parameters suggest minimal Co-C pi-bonding.
- Stronger Co-C bonds in vinylcobaloximes are attributed to increased s-character at carbon.
- Reduction potentials correlate with the pyridine ligand's electronic properties.
Conclusions:
- Co-C pi-bonding is not significant in these vinylcobaloxime complexes.
- The enhanced Co-C bond strength is primarily due to the high s-character of the carbon atom.
- Reductive Co-C cleavage proceeds via direct formation of the cis-1,2-dichlorovinyl anion.
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