7d Flashcards
describe cyclopentadieneeeee
its a pentagon with 2 double bondssss
and 2Hs coming from one of the points with no double bonds attached to it
what long.n can cyclopentadiene be
it can be n2 aka use of one double bond
or n4. use of both double bonds making all 4C’s dependent on one another.
what do u form when u remove one of the acidic H’s on cyclopentadiene
u form cyclopentadienyl
aka a pentagon with a circle and a - in the middle of the circle
whats cool about cyclopentadienyl anion,, describe it
its an n5 but its got 6e-!! meaning its aromatic
its also called Cp- aka C5H5
its a polymer ()n
when u have cyclopentadienyl anion,, what does it act like
its actts like an Me
aka when u have Li,, u get Me-Li and u get the cyclopentadienyl anion with Li where one of the H’s were
is cyclopentadienyl anion aromatic or not
its not aromatic
its a polymeric structure
what bond is the cyclopentadienyl anion and Li bond
its a pure sigma bond // sigma interaction
whats a Cp- ring
cyclopentadienyl anion riung
5C’s but 6e- so its aromatic
whats the Mos for Cp-
antibonding,, 2 nodes ,, 2 of these : delta backbonding from the dxy and dx2-y2 orbitals
bonding, 1 node, 2 of these: pi donation to the d orbitals: dzx, dzy,
bonding : 0 node, 1 of these, dz2 orbital
we have 6e- so all the bonding mo’s are filled.
bc we have 5 p orbtials from the 5 carbons in Cp-,, what do we get
we get 5MO’s
how do we make Cyclopentadiene
NaCP + BrMn(CO)5 —> Cp - Mn(CO)3 + 2CO + NaBr
or CP (n4) to Fe(CO)5 —–heat—-> CP-Fe,H,(CO)2 (this is an n5 and its stabilised to to its aromaticity.
it can dimerise when it loses H’s
how do we make ferrocene and what does it look like
2Cp + 2KOH + FeCl2 —> Cp-Fe-Cp + 2KCl + 2H2O
what type of compound is ferrocene
its a bis (cyclopentadienyl) metal complexes
okay so when we have a ferocene do we have Cp or Cp-
we have Cp-
bc theyre called bis(cyclopentadienyl) metal complexs
are therre different bis(cyclopentadienyl) complexes
and what varies between them if so
yes theres a bucnh of them
the metal and the bond length changes
the bis cyclopentadienyls can be what or what
and whats best about each thing
they can be eclipsed or staggered
staggered is better in terms of sterics but eclipsed is better in terms of orbital overlap
okay so when we had 1 cyclopentadienyl,, we have 5 mo ,, so when we have a bis cyclopentadienyl metal complex,, how many mo’s will we have
we have 10
5 for each cyclopentadienyl.
why do we have 5 mos split into 2 for the bis cyclopentadienyl and metal mo
bc u have 2 cyclopentadienyls!!!
and u have 5 diff ones bc u have 5 diff mos
aka 0, 1, 2, nodes. 1,0. 2,1 qnd 2,2 node ones which adds up to 5.
following where each orbital overlaps with,, we can fingure out which orbital it is.
u have 18 bonding ,, 1 nb and 10 antibonding.
thats why 18e- are normally preferred,,, bc u get to fill all the bonding mo,,, any more = antibonding get filled,,, any less=. not all the bonding mos are filled
when u have the biscyclopentadienyl structure,, how do they overlap with the metal complex
u need to draw the p orbitals on the first one,, then ether shade in the same ones on the other cyclopnetadienyl,, or shade it in the opposite way,, and then imagine putting diff metal s, p, d orbitals between them.
these overlap with the ao that could!! overlap correctly with the cyclic structure.
is 18e- the only cyclopentadienyl complex allowed
nope
its the most stable tho bc 18e- allows us to fill in all the 9 bonding mos
but other configs can be used
the bond length will differ tho
more e- than 18e-
antibonding orbitals get filled
u get longer bonds
less e- than 18e-
not all the bonding mos are filled
u get longer bonds
what ferrocene looking this is very easy to oxidise and why
cobaltocene is easy to oxidise
bc it has 1 outer electron,, which is easy to get rid of
bond lengths in bis(cyclopentadienyl ) reflect what
they reflect the population of bonding // antibonding orbitals
