plante1999 - 2-6-2012 at 01:41
Only for academic purpose.
Why Lead acetylide doesn not exist? Many acetylides are know but I never saw lead acetylide.
Thanks!!!
kristofvagyok - 2-6-2012 at 02:26
There was a few experiments preparing the title compound, but as far I know they were unsuccessful.
A method is described in Gmelin Handbook: Pb: MVol.C2, 166, page 697 - 699 where they tried to make it from Pb(Ac)2 and CaC2 in water/methanol but
they didn't isolate the lead carbide.
There are also other references for this comp. but as I see they were also unsuccessful:
Montignie, R.
Bull. Soc. Chim. France (5), 1935 , vol. 2, p. 1807 - 1809
Durand, J. F.
Comptes Rendus Hebdomadaires des Seances de l'Academie des Sciences, 1923 , vol. 177, p. 693 - 695
woelen - 2-6-2012 at 10:54
I'm not sure lead acetylide is not known, but in general indeed certain metal salts are not known. This does not mean that they cannot exist, it means
that there is no known preparative method for them. The most common reason for this is that these salts are combinations of easily hydrolysed metal
ions and a weak acid. E.g. iron(III) carbonate is not a known salt, because when Fe(3+) and CO3(2-) are brought in contact in solution, then
hydrolysis occurs, such as formation of [Fe(OH)](2+) and HCO3(-) and such hydrolysed species then form a precipitate. Iron(III) will almost certainly
hydrolyse so far that with carbonate ions it forms Fe(OH)3. Copper(II) forms a mixed copper hydroxide/carbonate, a so-called basic carbonate.
In the particular case of lead(II) and acetylide I can certainly imagine that this is not easily prepared from aqueous solution. Acetylide ion is
strongly basic and is very easily hydrolysed. The lead(II) ion also is easily hydrolysed. So, I foresee formation of Pb(OH)2 and H2C2. Acetylide also
is a somewhat special case, as it forms no purely ionic bonds with certain metal ions. The metal ions must have low oxidation state, such as Ag(+) and
Cu(+). I do not know copper(II) acetylide, only copper(I) acetylide. Maybe Pb(2+) has too high an oxidation state.
plante1999 - 4-6-2012 at 04:00
I know this theory but I did not know that lead II was easily hydrolised. Thanks! The same reason why titanium carbonate is really really difficult to
make and aluminium III + carbonate will make hydroxide of aluminium in place of carbonate.