[peterschmidt3943]

Hello,

I would like to know what the reason behind the following question is: why can't electron pair repulsion theory be used to predict the shape of the [CoCl4]2– ion ?


In the soultions, they stateted following: Too many electrons in d sub-shell / orbitals

Theoretically, that's wrong.
Electronic configuration of Co2+: 1s^2 2s^2 2p^6 3s^2 3p^6 3d^7. 15 Valence electrones from Co2+ + 4 + 2 =21 electrones in outside shell (right?). 21-8= 13

So the correct answer should be: too many lone paired electrones or: too many electrones in 3rd shell, right ?

[peterschmidt3943]

and can we also apply the inert pair effect on this question?

And furthermore: does the electronic configuration in Co as in [CoCl-]^-2 has to be written like Co(II), so 25, or like normal Co, so 27?

So, either (I): Electronic configuration of Co2+: 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^5 (I think I made a mistake in my first post, right?) or (II): Electronic configuration of Co: 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^7 ?

[peterschmidt3943]

could someone help me? I need the answer to pass my A-levels...

[Flatbutterfly]

It is found that the d electrons in TM cmpds are not stereochemically active.  For example, the aqua cmplxs [M(H2O)6]^2+/3+ {e.g.,  [Ti(H2O)6]^3+ , 3d^1; Cu(H2O]^2+, 3d^9} are all essentially octahedral.  (The Cu(II) cmplx ion is subject to Jahn-Teller distortion.)  Will this suffice?  I can go into possible reasons for this if you wish, but TM’s often have six or more oxdn states so the arguments are involved.
VSEPR theory should therefore only be used for main group cmpds (s and p bonding AOs).
http://en.wikipedia.org/wiki/VSEPR_theory
http://www.meta-synthesis.com/webbook/45_vsepr/vsepr.jpg

Inert pair effect effect only occurs for the heavier main group elements (Tl(I,III) Sn and Pb (M(II/IV))