Fe(η5-C5H5)2 does not react with hydrogen, but its nickel analogue, Ni(η5-C5H5)2 is readily hydrogenated to give Ni(η5-C5H5)(η3-C5H7). Use the 18 electron rule to explain this behaviour.
My answer so far...
Fe(η5-C5H5)2 18 electron rule = valence electrons from Fe is 8, electrons from C5H5 is 5 therefore 8 + 5 + 5 = 18 so it is stable.
Ni(η5-C5H5)2 18 electron rule = valence electrons from Ni is 10, electrons from C5H5 is 5 therefore 10 + 5 + 5 = 20 so Ni is not in most stable form
Ni(η5-C5H5)(η3-C5H7) 18 electron rule = valence electrons from Ni is 10, electrons from C5H5 is 5.....
how many electrons from (η3-C5H7) and how does this all explain why the iron complex doesn't react with hydrogen but the nickel one does? It is to do with the fact it has two too many electrons (20e) so it bonds with two protons from hydrogen? Also what does this symbol η mean?