High-spin configurations

IS readily obtained hy photolysis of a solution of (Relrj -CsMctl H) in pentane. It is low-spin at loss lemperatutes but has a minor contnbiuion frtim the high-spin configuration at ro m temperature ... 

Table 2.3. Calculated bond lengths and energies of first-row transition metal monofluorides in low-spin and high-spin configurations (an asterisk marks the spin multiplicity of lowest energyj...

If the coordination number of a given complex of a first row transition metal ion exceeds six there seems to be a general stabilization of the high-spin configuration. To our knowledge, there are no examples of Fe(II) crossover complexes with such high coordination numbers. 

Figure 5.7 gives the relation between isomer shift and quadrupole splitting for iron in various environments. In oxidic components of iron catalysts, one usually only encounters the high-spin configurations of Fe2+ and Fe,+ ions. 

Raman spectra were performed by Wang s group100. They found the heme to have a 5-coordinate high spin configuration. The fifth ligand was an axial bond to the thiolate, which was confirmed by the Fe—C—O bending mode at 562 cm-1. 

The lowering of symmetry in fluoride structures that contain Jahn-Teller ions instead of normal ones is explained this way. All cases of high-spin configurations d (Cr2+, Mn +) and (Cu2+) provide examples of distorted MeFa-octahedra. The overall distortion always leads to elongated octahedra, as accounted for theoretically by Opik and Pryce (234). 

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