Use of Electron Paramagnetic Resonance Spectroscopy to Study the Interaction Between Cobalt Schiff Base Complexes and Phosphines or Phosphites in Solution
EPR measurements on frozen solutions of a wide range of phosphine or phosphite adducts of CoII Schiff base complexes have given well resolved spectra exhibiting cobalt and phosphorus hyperfine structure. From analysis of the 31P hyperfine tensor, the R-P-R bond angle can be deduced in the phosphine or phosphite, PR3. The calculated spin densities in the cobalt and phosphorus orbitals allows a determination of the relative contributions of σ- and π-bonding in the Co-P bond and their influence upon the phosphine or phosphite bond angle. From a full analysis of the 31P polarisation tensor, a correlation is found between its magnitude and the magnitude of the splitting of the cobalt dxz and dyz orbitals. In analysing the 59Co spin Hamiltonian parameters, use is made of the theory of McGarvey and the approximations of Attanasio.
KeywordsElectron Paramagnetic Resonance Spin Density Hyperfine Coupling Polarisation Tensor Freeze Solution
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