Are there any compounds with pentavalent carbon?

1 Answer
Ernest Z.
Apr 20, 2015

Scientists first prepared methanium ion in 1950.

Explanation:

Methanium ion

Fluoroantimonic acid #"HSbF"_6# reacts with methane to form methanium ion, #"CH"_5^"+"#.

It is a fluxional ion, in which the #"C-H"# bonds are continually breaking and re-forming even at 4 K.

![https://phys.org/news/2015-03-shrew-scientists-decipher-spectrum-ch5.html](useruploads.socratic.org)

In the animation above, the black ball in the middle is the carbon atom, and the red and white ones are hydrogen atoms. The blue clouds represent the electron pairs.

A theoretical pentacoordinate carbon

Theoretical chemists have predicted that #"CBe"_5^(4-)# would have a planar pentacoordinate carbon and might even be stable in the gas phase.

mappingignorance.org

The bonds are not ordinary σ bonds. Instead, they involve various σ and π orbitals involving the whole molecule.

#"CAl"_4"Be"# and #"CAl"_3"Be"_2^-# are also theoretical possibilities.

pubs.rsc.org

Heptacoordinate carbon?

Another theoretical possibility is #"CTi"_7^(2+)#, with a #"C"# atom at the centre of a pentagonal bipyramid — a heptacoordinate #"C"# atom!

ACS Publications - American Chemical Society

Related questions
See all questions in Bonding
Impact of this question
5911 views around the world
You can reuse this answer
Creative Commons License