[coldest]

what does this word mean?
what is the ralationship between Ferrocenium and ferrocene?
 

thanks!

[AgG]

A google search will help greatly if you are in need of detailed information.

ferrocene has the formula Fe(C5H5)2  and cosists of two cyclopentadienyl rings coordinated to the iron center via "eta" 5 bonding.  The compound is quite stable owing to molecular orbital arguments (ie the 18 electron rule).  

ferrocenium is the positive ion of ferrocene where iron is in the +1 oxidation state

[coldest]

oh,oxidation number and oxidation state is so complex and made me crazy, but now i understand

but I don't know why the oxidation number of C5H5 is -1, also why the iron of ferrocene is stable because of 18 rule.

Fe 1s-2,2s-2,2p-6,3s-2,3p-6,3d-6,4s-2
so    2       8            14                2
how Fe2+ get 18 electrons from C5H5

many thanks! I am a beginner of coordination chemistry

[movies]

ferrocenium is the positive ion of ferrocene where iron is in the +1 oxidation state

Iron is formally +3 in ferrocenium and +2 in ferrocene.

[AgG]

yep.  mixing up my e counting.  Cp is definitely a -1 ligand so I stand corrected.

[AgG]

C5H5 (Cp) is the reduced form of cyclopentadiene C5H6. There are two ways to count electrons in organometallic compounds: the ionic model and the covalent model. The covalent model is currently favored as it makes no assumptions about the oxidation state of the metal so that the only information required is electron donor properties of the ligands and the ground state configuration of the metal.  18 electrons are accounted for in Fe(C5H5)2 like so:  The ground state of iron (Fe(0)) has 8 electrons in its outer shell (3d-6, 4s-2) and the Cp ligands donate 5 electrons each to the Fe center. 8 + 2*5 = 18.

The MO theory is a bit more involved (the theory is actually a LOT more involved) but may already be discussed in these forums.  With respect  to organometallic chemistry, Shriver and Atkins provide a good section in their "Inorganic Chemistry" textbook. There is also an oxford chemistry primer that gives an excellent introduction into MO theory if I remember correctly.

[coldest]

you are so strong!

I understand thoroughly this time. Thank you!!!