Bis-ir-cyclopentadienyl complexes

Ruthenocene and osmocene, however, crystallize in the eclipsed form. The C5H5 rings in w-cyclopentadienyl complexes are planar and all the C—C bond distances are equal. As will be seen later (p 219) they possess considerable aromatic character, and in favourable cases, e.g. ferrocene, undergo electrophilic substitution reactions such as acetylation. 

Cony ound assignments of only moment moment 

The sandwich bis-7r-cyclopentadienyl complexes are thermally rather stable, and many melt without decomposition at about 173X. They are stable to hydrolysis, and the C5H5 rings resist catalytic hydrogenation. Their stability to oxidation, however, varies greatly with the nature of the metal. At room temperature the 18-electron complex ferrocene is inert to molecular oxygen, whereas chromocene (which possesses a 16-electron configuration) is pyrophoric in air. 

In Table XV magnetic data for some metallocenes and metallocenium cations are listed. It can be seen that the experimental magnetic moments are, in many cases, close to those expected using the spin-only formula. 

Cobaltocene undergoes several interesting reactions in which the products attain the stable 18-electron configuration. As has been mentioned, this can occur by the loss of the unpaired electron to yield the cobaldcenium 

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The neutral bis-w-arene complexes form well defined crystals, moderately soluble in common organic solvents. They may be sublimed in vacuum at about 100°C. Thermally they are reasonably stable, frequently up to 300°C. Some mean bond dissociation energies of the metal-ring bonds are listed in Table XVI together with some equivalent data for bis-ir-cyclopentadienyl complexes. 

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