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New anionic cobalt complexes using highly hindered bis-amides with varying donor abilities as ligands
Claudio A Jiménez1, Julio B Belmar, Joel Alderete
1Dpto. Química Orgánica, Facultad de Ciencias Químicas, Universidad de Concepción, Casilla 160-C, Concepción, Chile. cjimenez@udec.cl
Dalton Transactions (Cambridge, England : 2003)
|May 22, 2007
Summary
New tetradentate ligands were synthesized and complexed with cobalt. The resulting cobalt complexes exhibit square planar cobalt(III) or low spin cobalt(II) species, depending on ligand structure.
Area of Science:
- Coordination Chemistry
- Organometallic Chemistry
- Materials Science
Background:
- Tetradentate ligands are crucial in coordination chemistry for stabilizing metal ions.
- Bis-benzamido ligands offer unique coordination environments.
- Cobalt complexes are of interest due to their diverse oxidation states and magnetic properties.
Purpose of the Study:
- To synthesize novel tetradentate bis-benzamido ligands.
- To investigate the complexation behavior of these ligands with Cobalt(II).
- To characterize the resulting cobalt complexes and determine their structural and electronic properties.
Main Methods:
- Ligand synthesis and characterization.
- Single crystal X-ray diffraction for structural determination.
- Spectroscopic (1H NMR) and magnetic susceptibility measurements for electronic structure analysis.
Main Results:
- Four tetradentate ligands (H(4)L(1)-H(4)L(4)) were prepared.
- Crystal structures of three ligands and one cobalt complex ([Co(III)(L(3))Na(I)(H(2)O)(2)]) were determined.
- Cobalt complexes 5-8 showed square planar Co(III) centers, while complex 9 exhibited a low spin Co(II) center.
- Magnetic and NMR data indicated an intermediate S=1 state for Co(III) in complexes 6-8.
Conclusions:
- The synthesized tetradentate bis-benzamido ligands effectively coordinate with cobalt ions.
- Ligand structure significantly influences the resulting cobalt complex's oxidation state and geometry.
- The naphthalene-based ligand leads to a weaker ligand field, favoring a low spin Co(II) complex.
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