[jak.berzelius]

So I have been assigned a problem to deduce structure of a molecule with formula and bonding sequence PSPS. The best I can come up with is a structure equivalent to the one found in 1,3-dioxetane (but with C swapped for P and O for S) https://en.wikipedia.org/wiki/1,3-Dioxetane. However in this structure the P-atoms don't have a full octet and begs the question if they would create a bridge towards each other across the structure or if some sort of resonance mechanism would occur.

or maybe this structure is completely wrong to begin with...

Anyhow, I've been stuck with this problem for a while and would really appreaciate any help I can get.

Regards


Ps. given how the problem was phrased i do not think thermodynamical aspects / stability have to be considered. Structure is the main focus.

[Orcio_87]

In my opinion there is bonding between P atoms in cyclic P2S2. I made some calculation in ORCA - P atoms are no closer than S atoms, but there is one orbital (second HOMO) which is bonding between the two P atoms. Almost rest of the orbitals cancels each other.

Molecule is planar.

[jak.berzelius]

In my opinion there is bonding between P atoms in cyclic P2S2. I made some calculation in ORCA - P atoms are no closer than S atoms, but there is one orbital (second HOMO) which is bonding between the two P atoms. Almost rest of the orbitals cancels each other.

Molecule is planar.

Thanks, man!

It feels good that you came to the same conclusion. However I'm still a little scepitcal wether or not this molecule would fit the "bonding sequence"  (PSPS) because of the p-p bridge.

What is your opinion on this?

[Orcio_87]

Calculations indicate that cyclic P2S2 is more stable than P-S-P-S.

I don't know if the difference is big or small since program doesn't display units of calculated energy (kJ, kcal....).

[Orcio_87]

As of P-S-P-S it is important that molecule is bend:

P-S
     \
      P-S

Linear P-S-P-S have more energy (is less stable).

But cyclic P2S2 is the most stable.

[jak.berzelius]

As of P-S-P-S it is important that molecule is bend:

P-S
     \
      P-S

Linear P-S-P-S have more energy (is less stable).

But cyclic P2S2 is the most stable.

Just to be clear, is this the structure you're suggesting?


S-S
I   I
P=P

[Orcio_87]

No, as this structure is far worse than linear and bend P-S-P-S and cyclic P2S2.