Cesium Trifluoride

[AbeMichelson]

I was thinking about this today, and, lo, so was someone else at some point eventually: http://www.scientificamerican.com/article/chemical-bonds-inner-shell-electrons/ . Non-valence electron bonding seems like it could be a new frontier of chemistry. The paper the article is based on is calculations. So what experiments could be run to actually make it?

High pressure has been suggested. Of course, there is probably not a single safe experiment

[Enthalpy]

Depending on what we want to call non-valence bonds, this can be less new than it seems.

 

In excimer lasers and lamps, exotic molecules are created, which can be extremely unstable, or stable enough to be stored for many minutes: Xe₂, XeF₂, ArCl₂ and many more. The rare gas used have no valence electron at all.

 

Transition elements show a fuzzy limit between valence and deep shells.

 

I vaguely suppose that metastable molecules, possible antibinding, form in the imploding bubbles during sonoluminescence.

 

Then, should we call it a chemical bond, if only pressure keep the atoms together? Squeezing atoms will necessarily modify the orbitals, and creating also molecular orbitals is rather natural under such conditions.

 

Easier to experiment than lithium trifluoride? Just take metallic lithium (very compressible), put pressure around it, observe if it shares more than one electron. Or try with rubidium instead. For instance the optical properties can be observed in a diamond anvil, and these will change, especially the optical frequency at which absorption augments.

[vampares]

Xe₂ et al. are not of chemical importance unless the existence of molecule is demonstrative of a principle of chemistry. That is really a malignant concept.

 

As for the cesium fluoride, the stoichiometry may favor double bond halogenation but fluorine is so strong that ... well it could work if the non-leaving group is chlorine.

[Enthalpy]

Excimers and rare gas fluorides demonstrate that chemical bonds can be made with a rare gas that has a full shell. Some are stable, and of technological importance. I suppose it's of interest to chemists as well, including if it doesn't fit simpler theories.

 

Could you detail what you call double bond and leaving group here?

[John Cuthber]

This seems a rather long thread considering that there's no actual evidence that the material exists (or ever will).

[AbeMichelson]

@John

If you count theoretical evidence, then that was the point of the post. There is evidence that it could. 2D materials were thought to be impossible before graphene (now we also have MoS₂ ).

@vampares

XeF₂ is actually a stable powder that sublimes. It has been used to fluorinate graphene. Also it is a great etchant for Si and is used in lithography because it preferentially etches Si over other materials.

@Enthalpy

Those are both Organic chemistry terms. If you have a reaction where one atom substitutes another, the substituted atom is the leaving group. Not relevant here because it describes covalent bonding (nonmetal-nonmetal). The double bond is simply 4 electrons shared by two atoms. Also, not relevant. Also, you have supposed that formed at high pressure means only stable at high pressure. There many minerals that were formed by the Earth's crust and meteor impacts that are stable at atmospheric pressure. Look at diamond.

Edited April 24, 2014 by AbeMichelson

[John Cuthber]

@John

If you count theoretical evidence, then that was the point of the post. There is evidence that it could. 2D materials were thought to be impossible before graphene (now we also have MoS₂ ).

 

If I do a calculation of the mass of a unicorn (by adding the typical mass of a horse to the mass of a narwhal horn) is that evidence that the unicorn exists?

At best the calculations are (some) evidence that the stuff might exist, not that it does, or that it will.

 

Also, I was doing research on 2D materials in 1987. It wasn't especially new.

The original work I cited was from 1919 if I remember correctly.

 

Now, can anyone tell me any measured property of CsF₃?

[AbeMichelson]

I meant 2D free standing, not monolayer. Unless, of course, the graphene literature stretches the truth (which would not surprise me) about being the first free standing 2D material.

1919, is that Langmuir himself? Katherine Blodgett's niece sent me an old film of Blodgett and Langmuir explaining surface chemistry...it's really cool.

 

I used to have the same attitude about computational chemistry, but a colleague changed my mind a few years back. Computational theory can point the way to interesting experiments, if the collaboration is strong. My point of introducing the topic was to explore possible strategies for making CsF₃, not to say it physically exists.

A few good links:

http://www.ch.imperial.ac.uk/rzepa/blog/?p=11681

http://www.nature.com/nchem/journal/v5/n10/full/nchem.1754.html?WT.ec_id=NCHEM-201310

 

The fact that the calculation was deemed worthy to be included in Nature, should lend a little more credence to the idea.