Hi!
The copper idea sounds good, but I think I found a nice solution of my tin problem, too:
tin(0) reduces tin(4) to tin(2) and becomes tin(2) itself... (at least this is my explanation for the following)
My idea was to start a SnCl
2 reduction with just a little bit SnCl
2 to get it going, lots of HCl and the right amount of elemental tin to generate enough tin(2)chloride for complete reaction. The following happened (I think): SnCl
2 gets oxidized to SnCl
4 while reducing something, but the elemental tin(0) already present immediately reacts with the tin(4) and, voila: two SnCl
2 molecules!! Which again reduce something, get oxidized to two SnCl
4 etc.
(you surely can imagine that the reduction done this way - with in situ SnCl
2 formation - is WAY faster than first forming tin(2)chloride and THEN using it to reduce something; the speed of rxn almost doubles with every molecule that is being reduced, and the generation of SnCl
2 also is a lot faster if the formed tin(2)-chloride is immediately oxidized, giving new tin(0) atoms a good opportunity to react with)
At least, a reduction to a propiophenone with SnCl
2 (not enough reducing agent; maybe 1:2 molar ratio tin(2)chloride/----), but with calculated extra amounts of HCl and tin(0) did require not significantly more time for completion than if 2.2x molar excess of reducing agent had been used - ca. 2,5 hours.
At the end of this time, all tin had been dissolved and a distinct color change indicated completion of reduction.
As you can see this is a bigĀ difference to just heating dil. HCl with tin(0) (many hours; not complete dissolution)...
I don't know if tin(0) really can reduce tin(4) to tin(2), but it would be a good explanation for what happened. What do you think?
Oh, and while on the topic of metal salts: why not regenerating elemental tin from SnCl
4 solution by adding zinc dust/HCl? The result would be fine Sn-sponge (best suitable for dissolving in HCl) and aequous acidic ZnCl
2 solution - urushibara-usable
!
Greetz A