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Asked by tangocharliee | 24th Nov, 2009, 10:40: AM

Expert Answer:

Ferrocene has a sandwich structure in which metal atom is sandwiched between two parallel cylcopentadienyl rings.The iron atom in ferrocene is normally assigned +2 oxidation state. Each cyclopentadienyl (Cp) ring is then allocated a single negative charge, bringing the number of -electrons on each ring to six, and thus making them  aromatic. Ferrocene is sometimes regarded as a compound of Fe2+ and two C5H5- ions.The twelve electrons (six from each ring) are then shared with the metal via covalent bonding, which, when combined with the six d-electrons on Fe2+, results in the complex having an   18 electron noble gas electron configuration. Bonding in ferrocene is better considered as pi -bonding involving lateral overlap of dxz and dyz orbtials on Fe with delocalized p- orbitals from cyclopentadienyl ring. The lack of individual bonds between the carbon atoms of the Cp ring and the Fe2+ ion results in the Cp rings to freely rotate about the Cp-Fe-Cp axis.

The general opinion is to consider ferrocene a six coordinate species because there are six electron pairs on the ligands that participate in bonding.

 

Symbol eta denotes the number of carbon atoms bonded to a metal. Since all five carbon atoms in cyclopentadienyl ring are equidistant from Fe, ring has hapticity  eta  of 5.

Answered by  | 25th Nov, 2009, 10:47: AM

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