Quad Bond

[_wolfgang_]

Main Question or Discussion Point

I am wandering whether this can happen? When a molecule shares 4 pairs of bonded electons? Say like a C₂ Molecule?? maybe. Could it happen or does it happen??

 

[Char. Limit]

Yes, but not for carbon.

The reason carbon can't four-bond is because of its tetrahedral geometry. Even with only half of the orbitals hybridized, one orbital on each carbon atom will still face "away" from the bond.

As it turns out, quadruple bonds, pentuple bonds, and even a sextuple bond have all been observed. Where? Metal-metal bonds in complexes, especially the heavier metals with loose electrons. I believe Tungsten and Rhenium both exhibit this odd behavior.

My theory as to why this happens? d-orbitals.

 

[Ygggdrasil]

My theory as to why this happens? d-orbitals.

Correct. Overlap between d-orbitals in metal-metal covalent bonds can produce a delta bond which is required to explain quadruple bonding species.

 

[Char. Limit]

Haha! I knew it!

Thanks for proving me right. Honestly, sometimes physics is so screwed up I think the intuitive answer, though right in this case, could ever be correct.

 

[DrDu]

Specifically I remember about some Rhenium and Technetium compounds with a formal Re-Re or Tc-Tc double bond.

 

[Char. Limit]

Doesn't mean it can't be higher as well.

 

[_wolfgang_]

Hmm so can actually happen just not with carbon, i get why now because of its tetrahedral shape. Also is there any special names for these substances, as well as would you know what the most amount of bonds there are possible?

 

[Char. Limit]

I don't know about the names, but I can tell you that the highest order bond observed is a sextuple bond, sharing 12 electrons.

 

[_wolfgang_]

Ok cool i see this happens molybdenum. Also what would happen to phsical properties? ultra hard? Ultra unreactive?