helium and neon ionic compounds

[insane_alien]

my inorganic chem lecturer informed us today that while no neutral compounds containing helium and neon have been discovered there are a few ionic compunds containing these elements. anybody know any of their chemistry? i assume that they are prety unstable

[silkworm]

I am aware of no compounds at all of Helium or Neon but I am aware of compounds with Xenon and Krypton with Flourine and Oxygen.

 

Dr. Neil Bartlett did this accidentally in the 1950s.

 

Xe(g) + 2PtF(6)(g) --25ºC--> [XeF+][PtF6-] + PtF(5) --60ºC--> [XeF+][PtF(11)-]

 

Later a group at Argonne National Laboratory did this:

 

Xe(g) + 2F(2)(g) --400ºC, 6atm--> XeF(4)(s)

 

This compound is the most stable noble gas compound but reacts explosively with water.

 

There are also a few other compounds involving Xenon flourides and Xenon oxides and even XeO(2)F(2), but all are very reactive. There is also a Krypton flouride. There is a radon difluoride that forms spontaneously at room temperature, but no one is researching it because radon is very radioactive.

 

There has been evidence via spectroscopy of HeH+, ArH+, He(2)+, Kr(2)+, NeXe+, and Xe(2)+ but none of these are stable at all and who knows if this is a chemical reaction or just some other sort of physical phenomenon, I sure don't.

 

I'm curious about Xe and Kr myself, and hopefully will experience them soon in solid form.

 

(Information for this post was taken from Descriptive Inorganic, Coordination, and Solid State Chemistry by Glen E. Rodgers, which I reccomend for anyone interested in inorganic chemistry).

[woelen]

my inorganic chem lecturer informed us today that while no neutral compounds containing helium and neon have been discovered there are a few ionic compunds containing these elements. anybody know any of their chemistry? i assume that they are prety unstable

The ionic compounds you are referring to only exist as transient species in very dilute gaseous form. By applying high voltages and sparks on a very low pressure mix of helium, neon or argon, people have succeeded to make trace amounts of ions of these gases, which however, only have a fleetingly short period of existence and react immediately with each other and with the environment, forming the normal mono-atomic gas again.

[insane_alien]

the ions he mentioned were think like HeH+ but there were 3 for He and a few more for Ne. I'm aware of the chemistry for Xe and Kr. i've seen pictures of solid XeF2, XeF4, XeF6 and XeO2. never seen the stuff in real life though. would be pretty cool. /me realises what a chemistry geek he is

 

just seen woelens post: ahh i thought they might have been longer lived than that. oh well.

[woelen]

just seen woelens post: ahh i thought they might have been longer lived than that. oh well.

It might be that in deep space such species exist for a longer time. In the very very dilute high vacuum space, where atoms and ions are very sparse, and where there is no matter to interact with, such ions may exist for a longer time, but on any earthly condition they only exist for milliseconds at best. No, there is no ionic species or whatever species of He or Ne which can be kept in a bottle, not even for minutes. For Ar, I believe there is some known compound, which exists at a few degrees K and can be kept under those conditions in an inert frozen matrix.

[RyanJ]

Doesn't Mercury form "compounds" with all of the noble gases? Although I say "compounds" they are thought to only be held together by the weak intermolecular van der walls forces and so do not really could as compounds I guess.

 

Interesting how Helium should probably be called Helion though

 

Cheers,

 

Ryan Jones

[woelen]

In fact, all noble gases form "compounds", which even have a distinct formula. A well known "compound" is C6H4(OH)2.Ar

 

This is a so-called clathrate. C6H4(OH)2 is hydroquinone (p-dihydroxybenzene). When a solution of hydroquinone in water is allowed to evapotate slowly in an atmosphere of argon under high pressure, then argon atoms become trapped in holes of the crystal lattice of hydroquinone. So, this is not a chemical compound, but a physical compound. The holes in the crystal lattice of hydroquinone are sufficiently large to contain a single atom of argon. If such crystals are added to water, then they dissolve and bubbles of argon escape again.

 

Clathrate compounds are quite common. Methane molecules can be trapped in a crystal lattice of water (ice) and this "hydrated" methane exists in large quantities at the bottom of the oceans. Yet another example is "hydrated" chlorine, Cl2.8H2O. This is chlorine, trapped in a crystal lattice of water (ice) and it can be made by freezing water in a chlorine atmosphere at 3 atmosphere pressure at a temperature of a few degrees below zero C.

 

Even more interesting clathrate compounds (a.k.a. cage-compounds) are derived from fullerenes, C60. Such a fullerene molecule, which has the shape of a soccer-ball is hollow. Inside, a small molecule or atom can be trapped and indeed, such compounds have been made, e.g. C60.Au.

[RyanJ]

Interesting woelen - never knew that one

 

Doesn't ammonium fluoride form a stable solution in ice on that note :S

I also read that the Noble gases cna do the same as you have described with water in the form of ice

 

Cheers,

 

Ryan Jones