[Anders Hoveland]

The traditional route to making SiCl4 and SiI4 is to burn elemental silicon with the halogen. While this route is very direct, it requires very high temperatures. It can also be difficult to obtain the silicon to begin with since silica can only be reduced with carbon in an electric furnace.

Here is an interesting new alternative:

Dissolving CaCl2 into molten zinc chloride (which melts at only 292 °C ), then bubbling in SiF4 (made by reacting silica with hydrofluoric acid). Anhydrous aluminum trichloride has an even lower melting point, 192.4 °C (this surprising number is not an error!)

(2)CaCl2 + SiF4 --> (2)CaF2 + SiCl4

The silicon tetrachloride could then be combined with sodium iodide and used just like anhydrous HI for most reaction purposes.

ZnCl2 can be made by passing dry chlorine gas into ethyl ether with a piece of metallic zinc. The ZnCl2 that forms actually dissolves in the ether. It might work for aluminum also. "Solutions of Aluminum Chloride in Ethers", Gordon G. Evans, Thomas R. P. Gibb Jr., J. Kevin Kennedy, Frank P. Del Greco
J. Am. Chem. Soc., 1954, 76 (19), pp 4861–4862


Aluminum triiodide melts at 189.4 °C, so if this was used as the solvent, silicon tetraiodide could be obtained.

(2)CaI2 + SiF4 --> (2)CaF2 + SiI4

The formation of calcium fluoride is driven by the fact that it is so insoluble, having such a high crystal lattice energy. Otherwise, of course, the reaction would be just the opposite.

Silicon tetraiodide could be dissolved in chloroform, then reacted with a limited quantity of water to form anhydrous hydrogen iodide.

SiI4 + (2)H2O --> SiO2 + (4)HI

It is interesting to note that SiF4 has much less of a tendancy to hydrolyse in water than the other silicon-halogen compounds.

(3)SiF4 + (4)H2O <==> (2)H2SiF6 + Si(OH)4

Indeed, although it is a very well known reaction, it is otherwise quite exceptional that hydrofluoric acid can react with silica. Silicon tetrafluoride is a gas.

SiO2 + (4)HF --> SiF4 + (2)H2O


Does this idea seem like it would be feasible? Do you think it would be practical?

[mississippichem]

Any prep involving HF falls off my list of "practical preps".

Im not a big fan of molten salts really either.

[Anders Hoveland]

mississippichem, on 25 December 2011 - 01:35 AM, said:

Any prep involving HF falls off my list of "practical preps".

Im not a big fan of molten salts really either.

Obviously one would need some plastic containers and tubing (available at a hardware store) to handle the HF and SiF4 gases, and a metal container for the main reaction.

Something like this could easily handle the HF, see the plastic container and tubing in the below page:
https://sites.google...ical/exeriments

The last part of the tube should be attached to a metal pipe so that it can buble the SiF4 into the molten salt, since plastic would otherwise melt.

This post has been edited by Anders Hoveland: 25 December 2011 - 08:59 AM

[hypervalent_iodine]

I'm sorry, but molten salts + HF? This isn't really something you should be attempting at home and is considerably less practical than the conventional route you've cited. How high is very high, anyway? And for the love of Woodward, start reading some papers published after last century.

[Enginer]

[quote name='Anders Hoveland' timestamp='1324803261' post='646893']
This is interesting to me. Anders, how may I communicate directly with you? Is your "receive email from other members" checked?


Pure SiCl4 has lots of uses and SiF4 usually has to be disposed of by recycling into H2SiF6, a "drug" on the market.




=>jim<=

Enginer

[Phi for All]

Enginer, on 9 March 2012 - 02:08 PM, said:

This is interesting to me. Anders, how may I communicate directly with you? Is your "receive email from other members" checked?


Pure SiCl4 has lots of uses and SiF4 usually has to be disposed of by recycling into H2SiF6, a "drug" on the market.




=>jim<=

Enginer

!

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