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Hybridisation of Mn in MnO4-

by jd12345
Tags: hybridisation, mno4
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jd12345
#1
Feb6-12, 11:56 PM
P: 260
What is the hybridisation of manganese in MnO4-
Configuration of manganese in 3d5 4s2 right? The paired electrons in 4s become unpaired - electron frm it jumps into the 4p orbital
So now configuration looks like this - 3d5 4s1 4p1
Now manganese forms 4 sigma bonds and 3 pibonds so the hybridisation should be d2sp and the three d-orbitals form pi bonds
But apparently this is not the case - hybridisation is sp3
I dont understand how - it doesnt even have 3 unpaired electrons in p-orbital
Do the electrons from d-orbital jump to the p-orbital?? But why should they?
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DrDu
#2
Feb7-12, 02:55 AM
Sci Advisor
P: 3,555
Why shouldn't they jump to the p orbitals. All d, s and p orbitals are nearly degenerate energetically and the electrons distribute so as to minimize energy. You also did take it as granted that the s electron may jump to a p orbital.
The problem is that when you want to describe bonding in MnO4- by Valence Bond theory you do have to consider resonance between dosens of structures, not only one. Many of them being ionic ones with electrons jumping from Mn to O or the other way round.
In this situation, it is hardly useful any more to use hybridized orbitals.
Promoting d electrons to the p orbitals and forming then sp3 hybrids is maybe a possible first approximation. Then you get at least the sigma bonds to the O atoms and you can use the d orbitals for pi bonding.
jd12345
#3
Feb7-12, 03:03 AM
P: 260
Yeah - but cant the d-orbital electrons form the sigma bond
Why do they jump to the p-orbital(increase their energy) and then bond.
They could have stayed in the d-orbital and 2 electrons could have formed sigma bond and other 3 pi bond

DrDu
#4
Feb7-12, 04:06 AM
Sci Advisor
P: 3,555
Hybridisation of Mn in MnO4-

You can also use sd3 orbitals or something in between sp3 and sd3. However, this is all quite speculative. However I would like to see a calculation from the last 30 years at least for confirmation and there is very little available. I would consider this kind of description of transition metal complexes as quite outdated.
jd12345
#5
Feb7-12, 09:54 AM
P: 260
@ DrDu
Sorry i didnt understand - what is outdated?


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