Cyclopentadienyl complexes magnetic susceptibility

An approach other than steric hindrance has been used to overcome the previously mentioned instability of the actinide homoalkyls. It was found that the inclusion of jT-bonding ligands in the coordination sphere considerably enhanced the stability of the alkyl complex. Recently, the same line of reasoning has also yielded a new series of 7r-cyclopentadienyl lanthanide alkyls (C5H5)2LnR where Ln =Gd, Er, Yb and R = C=C, and CH3 120,121). The infrared data for these complexes are consistent with u-bonded structures and the room temperature magnetic susceptibilities are very close to the free ion values. The actinide complexes (75,... 

Many cyclopentadienyl complexes contain partially filled electron shells. Therefore, such compounds are paramagnetic. The magnetic susceptibility may also be influenced by the orbital momentum which may increase the magnetic moment. Table 9.5 gives magnetic properties of some cyclopentadienyl compounds. 

This behavior is even more pronounced in the complex Mn(C5H4Me)2, for which a small energy difference between these terms was observed in solution based on the measurements of magnetic susceptibility as a function of temperature. They proved that there is an equilibrium between the high- and low-spin form of the compound which is temperature dependent. Photoelectron spectra of some cyclopentadienyl complexes are given in Table 9.7. 

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