Inorganic I - 8 Coordinate Complexes

  • Thread starter Thread starter Nezva
  • Start date Start date
  • Tags Tags
    Coordinate
AI Thread Summary
The discussion centers on the existence and classification of 8-coordinate complex point groups, specifically addressing whether such complexes exist and their symmetry properties. The point group for these complexes is identified as Oh, which is also applicable to 6-coordinate complexes, leading to some confusion due to their differing structural arrangements. The conversation highlights examples of 8-coordinate complexes, such as the XeF8 2- anion and ZrO8, noting that they can adopt geometries like square antiprisms and dodecahedra. It is emphasized that octahedral and cubic arrangements share the same symmetry due to their dual relationship, where an octahedron can be inscribed in a cube and vice versa. The discussion also touches on the visual complexity of these structures and the challenges in understanding their symmetry.
Nezva
Messages
46
Reaction score
0
Main question: What is the name of the 8 coordinate complex pointgroup? Or does it even exist?

I've been exposed to octahedrons and icosohedrons, however, the 8 coordinate high symmetry complexes appear to have been skipped. I'm aware that these complexes would be rare but I think that they do exist. I was able to find this image of a XeF8 2- anion:
http://ce.sysu.edu.cn/echemi/inocbx/ic3/Xe/images/XeF8_2-.jpg

Another visual representation is the f-orbital (xyz)... if the lobes were treated as not having spins (all the same "ligand").
http://en.wikipedia.org/wiki/File:F4M2.png
 
Chemistry news on Phys.org
For a coordination number of 8, either a square antiprism (like the XeF82- and IF8- anions) or a dodecahedron (ZrO8) can be formed.
 
In square antiprism the squares to not overlay each other, they are staggered 45 degrees. But thank you for showing me antiprisms, very neat structures to try to do molecular symmetry on.
A dodecahedron has too many coordinates from what I see but also an interesting structure.

The pointgroup is Oh, which confused me because there is a 6 coordinate version of the Oh pointgroup. For anyone having the problem I had... The 6 coordinate Oh complex has 3 sigma-h along 5 atoms (4 ligands and center), while the 8 coordinate has 3 sigma-h in between bonds (only intersecting the center atom). Visually, I had a lot of trouble believing they were both the same pointgroup.
 
So you don't seem to be interested in all 8 fold coordinate complexes but in those with a cubic arrangement of the ligands.
The cubic and the octahedral coordination have the same symmetry because they are dual to each other: an octahedron can be inscribed into a cube so that the corners of the octahedron coincide with the centers of the faces of the cube. This works also the other way round. The same relation holds for an icosahedron and a dodecahedron which have both symmetry group I_h. The tetrahedron is dual to itself.
 
It seems like a simple enough question: what is the solubility of epsom salt in water at 20°C? A graph or table showing how it varies with temperature would be a bonus. But upon searching the internet I have been unable to determine this with confidence. Wikipedia gives the value of 113g/100ml. But other sources disagree and I can't find a definitive source for the information. I even asked chatgpt but it couldn't be sure either. I thought, naively, that this would be easy to look up without...
I was introduced to the Octet Rule recently and make me wonder, why does 8 valence electrons or a full p orbital always make an element inert? What is so special with a full p orbital? Like take Calcium for an example, its outer orbital is filled but its only the s orbital thats filled so its still reactive not so much as the Alkaline metals but still pretty reactive. Can someone explain it to me? Thanks!!
Back
Top