Properties of Cyclopentadienyl Complexes

Sandwich complexes Mcp2 are thermally very stable. They melt at relatively high temperatures, usually without decomposition. The resistance of metallocenes to oxidation varies. Some are completely air stable, for example, ferrocene and ruthenocene. However, some are pyropophoric, such as chromocene and vanadocene which spontaneously inflame in air. Often during controlled oxidation, oxo 7r-cyclopentadienyl complexes are obtained. 

All metallocenes are oxidized to the Mcp2 cations in acidic media. Sometimes this reaction is reversible. Many complexes become protonated to give Mcp2H in acidic solutions. Numerous cyclopentadienyl compounds which also possess other ligands coordinated to the metal are known, for instance, halogens, CO, H, OH, O, etc. Also, the formation of cyclopentadienyl polynuclear and cluster complexes is well known. 

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Table 9.5. Magnetic Properties of Cyclopentadienyl Complexes of Transition Metals ...

Cyclopentadienyl compounds of this group are most commonly obtained by the reaction of Nacp with metal halides MC1 . Some properties of cyclopentadienyl complexes of the vanadium group are presented in Table 9.10. The properties of [Mcp(CO)4] are given in Chapter 2. 

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