In $\ce{SO5^{2-}}$, can somebody tell me which orbitals are used to form the pi bonds in this anion. Please tell the hybridization. And the lewis structure.

Well I tried and the answers I got was sp3 & the pi bonds are formed using d orbitals.I just need to know whether I'm correct

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    – Philipp
    Dec 3 '14 at 21:09

Here is already the Lewis structure

Here is already the Lewis structure

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    $\begingroup$ I see, sorry I'm rather new on the website, I just wnted give a little help :x $\endgroup$
    – Babounet
    Dec 4 '14 at 7:27

The peroxomonosulfate is a hypercoordinated molecule, in which the sulfur appears to exceed Lewis' rule of two, better known as the octet rule. In former times it was believed that d orbitals would contribute to bonding. This is not the case.
Bonding is better represented by

  • three equivalent $\ce{S-O}$ single bonds
  • sulfur having a formal charge of +2
  • these three oxygens having a formal charge of -1
  • one $\ce{S-O}$ single bond that leads to the peroxyl oxygen
  • this oxygen has a formal charge of zero
  • one $\ce{O-O}$ single bond
  • and the terminal oxygen having a formal charge of -1

This bonding picture is much more in accordance with quantum chemical calculations and an NBO analysis on the DF-BP86/def2-SVP level of theory. The involvement of d orbitals is minimal (<1%).
enter image description here

It is noteworthy, that this molecule pretty much has the same bonding around the sulphur as in sulphate. It can therefore similarly be described. Have a look at my rant against hypervalency or the bonding picture of the $\ce{PO4^{3-}}$ anion, which is isoelectronic to sulphate.


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