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I was doing lewis structures and i came across a question asking the structure of POCl3. Here, the answer is a tetrahedral shape with P as central atom connected to 3Cl atoms by a single bond and 1 oxygen atom by a double bond. The valency of P is 3. So, it needs 3 electrons to get the nobel gas configuration and become stable so it could have formed single bonds with 2 cl atoms and single bond with an oxygen atom which would be single bonded to cl atom. Why isn't this structure correct?

And how can P form 4 bonds while it needs only 3? I think it's something related to D-orbital but if it undergoes sp3d hybridisation, it would need 5 bonds. Also, the structure of this compound is tetrahedral and hybridisation of P is sp3. How can this be? How can it form 4 bonds although it has only 3 unpaired electrons? Nitrogen couldn't form such compounds.

I googled about it and could find nothing but the hybridisation and lewis structure. My actual question isn't answered anywhere

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  • $\begingroup$ I unfortunately have no time to answer this, here are a few notes though. The phosphorus is hyper-coordinated in this structure. Think about which element is the most electronegative, try charge separation. It has been disproven that d-orbitals play a significant role in such compounds, better not learn about this. Hybridisation is not a concept that can be used for prediction, it is quite visual for interpretation though. $\endgroup$ – Martin - マーチン♦ Jan 15 '17 at 12:12
  • $\begingroup$ Think of it as $\ce{[POCl2]+[Cl]-}$. Still a wrong picture, though. You'd need resonance. $\endgroup$ – DHMO Jan 15 '17 at 14:56
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    $\begingroup$ Have a look at "Phosphoryl chloride" on Wikipedia and the article "Hypervalent molecule" linked from it. $\endgroup$ – SteffX Jan 15 '17 at 16:05
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    $\begingroup$ There should be a duplicate lying around here somewhere … Basically, don’t use d orbitals unless your at school and your teacher tells you to. And if that is the case, forget it the moment you leave school. Instead, you can think of $\ce{\overset{+}{P}-\overset{-}{O}}$, i.e. charge separation. Also, @DHMO’s description is wrong in this case; charge separation is a more simple and better description. 4e3c bonds are only required for pentacoordinated phosphorus atoms. $\endgroup$ – Jan Jan 15 '17 at 22:27
  • $\begingroup$ I'm still not able to get the correct picture. $\endgroup$ – Tejesh Atr Jan 26 '17 at 6:00