Crystal Field Theory: Square Planar Complexes - Video Tutorials & Practice Problems
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1
concept
Square planar complexes show the most complex splitting pattern.
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Square planar complexes show the most complex splitting pattern. We're gonna say orbitals on and between the X and Y axes have the strongest interactions with ligands. Remember the stronger the interaction with the ligands, the higher the energy of the orbital. If we take a look here at this image, we can see that there's a gradient that forms with the first three orbitals. It starts off very shaded initially and then it tapers off and gets lighter as we move towards the right signifying a lesser interaction with the ligands and therefore lower energy for orbitals. The first one makes sense because in this one, we're dealing with uh interactions that are on or along the axes, the X axis interacts with two lobes here as it cuts through. And then the Y axis interacts with two lobes as it cuts here. The next one should have the second highest energy because it interacts with both X and Y axis still just not as much as the first one DZ squared might seem misplaced here. But there is some interaction occurring with the X and Y axis. If you look closely, you'll see this ring or kind of dis this one lies and interacts with the X and Y axis. If you look, you can see the Y cutting through it and here you can see the X cutting through it. So it's along the axis, it just doesn't have as great interaction as the previous two orbits. So that's why it's here. The last two, they are degenerative, they have the same energy because they're each only interacting with one of the two axis that we care about. X and Ydyz is interacting with the Y axis and DXZ is interacting with the X axis. Now, as you can see, this crystal field splitting pattern is pretty tall and the difference in height here is why square planar complexes have the largest delta values. Now again, their spleen pattern is a bit more complex. But as you go through each one and see how they interact on the or with the X and Y axis, it all starts to make sense.
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example
Example
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Which one of the following complexes shows the most complex splitting pattern energy. Remember this occurs with square planar complexes. If we look at our options, B and D are both out because in both we have six donor atoms connecting to our metal cion, those could not give us a square planar complex. The answer is gonna be either A or C because in both of those, we have four lions which have the potential of being either tetrahedral or square planar. In the first one, if we take a look at the cadmium ion, it's cadmium two plus it's electron configuration when you look at it would be krypton four D 10. Now here it is ad 10 ion. And remember if you're D 10, you are tetrahedral. So this would not give us the correct geometry for C. We have nickel here connected to four ammonia which are neutral. So the two plus charge is coming from the nickel itself. If we do its electron configuration, it would be argon 3d 8. Now it is ad eight ion and that means that its geometry is square planar. So option C would give us a squared planar geometry which results in the most complex splitting pattern energy.
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Problem
Problem
Which of the following complexes will have the largest crystal field splitting energy?
A
[Co(NH3)6]2+
B
[Cr(NH3)3(H2O)3]2+
C
[ZnCl4]2–
D
[Ni(CN)4]2–
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