Competition - post a photo you've taken of nature >>

Reactions of Tin (IV) halides

Inorganic chemistry is driving me up the wall. I've been to the library, and searched on the internet for SO many hours, but I can't seem to find what happens between Tin (IV) halides and triphenylphosphine. Now, I know the Tin (IV) halides are lewis acids, but I can't quite find any decent resource on the reaction between them and triphenylphosphine, other than the rather vague they form (SnX_4)(PPh3)_2

Tantalizingly, http://www.tulane.edu/~inorg/Lab%20Manual/Experiment%202.pdf has something about: Complexation, or "adduct"-forming reactions. To a solution of 2.0 g triphenyl phosphine in
2 ml benzene, add a solution of 0.5 g of SnCl4 in 2 ml benzene. Repeat this reaction with
0.5 g SnI4. How does the reactivity of SnCl4 change as a result of forming a complex with
Ph3P?
(e) Although SnCl4 will react with triphenylphosphine, CCl4 is unreactive in this regard.
Explain why this is so.

But I can't seem to find anything about the answers. :frown:

Reply 1

shengoc

Lifeisnice

Have you tried greenwood and earnshaw chemistry of the elements or advanced inorganic chemistry by cotton and wilkinson?

Reply 2

Lifeisnice

shengoc

Have you tried greenwood and earnshaw chemistry of the elements or advanced inorganic chemistry by cotton and wilkinson?

I think I did, but they didn't have anything other than the reactions with water or the adding of X-? Even the multivolume books on inorganic chemistry can't have all the reactions. :frown:

In fact, they don't really talk about the experimental observations, such as precipitates. :s

Reply 3

shengoc

Lifeisnice

I think I did, but they didn't have anything other than the reactions with water or the adding of X-? Even the multivolume books on inorganic chemistry can't have all the reactions. :frown:

In fact, they don't really talk about the experimental observations, such as precipitates. :s

I am not really sure, but if TiX4 is a lewis acid, and PPh3 is a lewis base, then it'd be simple lewis acid - lewis base interaction, ie dative covalent bonding, just like NH3 and BF3.

Reply 4

Kyri

shengoc

I am not really sure, but if TiX4 is a lewis acid, and PPh3 is a lewis base, then it'd be simple lewis acid - lewis base interaction, ie dative covalent bonding, just like NH3 and BF3.

I agree with this. The lone pair on phosphorus coordinates to the vacant 5d orbital on the tin atom. This happens twice to get SnCl4(PPh3)2. This is very similar to NH3 and BF3, the only difference being the nitrogen lone pair goes into an empty p orbital on boron.

I'm just speculating here, but I suspect SnCl4(PPh3)2 will be less reactive than SnCl4 and less moisture sensitive as the PPh3 ligands are taking up coordination sites so the 5d orbital will be less accessible. As such, associative mechanisms will be less likely. Dissociative pathways might be required to make room for a reacting species, such as H2O, so reactions should be slower, including hydrolysis by water vapour in the air. Again, I'm just speculating. I don't know any of this stuff for a fact.

I can tell you for sure why CCl4 doesn't react with PPh3 though. The electronic configuration of sp3 hybridised carbon is 1s2 2s1 2p3. The next accessible d orbital is the 3d orbital which is too high in energy compared to the lowest occuped orbital (2p). For tin, the configuration of its sp3 hybridised state is [Kr] 5s1 4d10 5p3. The 5d orbital is much closer in energy to the 5p orbital than the 3d is to 2p so its much more feasible for it to accept electrons from a lewis base. Hence, SnCl4 will react with PPh3 but CCl4 won't.

Reply 5

shengoc

I just recalled that PPh3 does react with CX4 where X = Cl, Br usually, it is called the appel reaction, converting R-OH to R-X.

The first step involves forming carbanion of CX3- and PPh3X+. But this would probably be reversible if no alcohol is introduced.