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  Preparation of Lead (IV) Acetate,  Pb(CH3COO)4 - Posted by Cherrie Baby
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           Handbook of Preparative Inorganic Chemistry, Volume I,
           2nd Ed. 1963 Academic Press, Ed Brauer, pages 767-769.
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 Pb3O4  +  8 CH3COOH  ==>  Pb(CH3COO)4  +  2 Pb(CH3COO)2 (*3 H2O)  +  4 H2O

 685.6       480.4         448.4             758.7                     72.1


                    4 H2O  +  4 (CH3CO)2O  -> 8 CH3COOH

                      72.1       408.4          480.4


          2 Pb(CH3COO)2 (*3 H2O)  +  Cl2  -> Pb(CH3COO)4  +  PbCl2

            758.7                   70.9     443.4           278.1

The reaction of Pb3O4 with CH3COOH is carried out in a one-litre, three-neck
flask fitted with a sealed stirrer and a thermometer; the third opening may
be closed (not too tightly). The required amount of pure Pb3O4 is finely
pulverised in advance, dried at 200°C and left in a desiccator over P2O5
until needed. The flask is charged with 550 ml. of glacial acetic acid and
170 ml. of pure acetic anhydride; the mixture is heated to 40°C, and then
300 g. of Pb3O4 is slowly added with vigorous stirring without further
external heating. During this procedure, the loosely fitting stopper is
removed, but only for brief periods. The reaction is exothermic and the
rate at which the Pb3O4 is introduced is regulated so that the temperature
in the flask remains under 65°C. Otherwise, the freshly formed lead
tetraacetate is partially reduced by the acetic anhydride. Running water
may also be used to prevent overheating of the flask. After most of the
Pb3O4 has been added, the temperature gradually falls, and toward the end
of the reaction it may be necessary to heat the flask (but never over 65°C).

The clear solution is left to cool protected from atmospheric moisture, and
large quantities of colorless Pb(CH3COO)4 precipitate out. The supernatant
liquid is decanted, and the precipitate is poured into a large Buchner
funnel. The funnel is covered with a cardboard square or a tile to minimize
the effects of atmospheric moisture during the very slow suction filtration.
The filter cake is washed several times with glacial acetic acid and dried
on a clay tile in a desiccator. The resulting product, usually tinted rose
or brownish because of the presence of small amounts of PbO2, can be
further purified by recrystallization from hot glacial acetic acid. Even
after prolonged desiccation a small amount of glacial acetic acid will be
retained by the salt. The yield is about 150 g.

Another, less pure quantity of the salt may be recovered from the mother
liquor, which is treated in the original reaction flask with dry Cl2 at
80°C until no further PbCl2 precipitates. Good stirring must be used. The
precipitate is filtered hot and washed with glacial acetic acid, and the
solution is left to crystallize. During cooling, about 100 g. of
Pb(CH3COO)4 crystallizes out. However, it is contaminated with PbCl2. Pure
lead tetraacetate can be obtained by repeated further recrystallization
from glacial acetic acid.

The procedure may be varied by omitting the acetic anhydride (Dimroth and
Schweizer). In this case, however, the maximum temperature must be held
below 60°C since the water formed in the reaction is not bound and may
hydrolyze the Pb(CH3COO)4 at higher temperatures.

Lead (IV) acetate may be stored only if absolutely dry and when kept in
well-closed ground glass bottles. It is used as a selective oxidant in
organic syntheses.


SYNONYMS:

Lead tetraacetate, plumbic acetate.


PROPERTIES:

Colorless prismatic crystals, very sensitive to moisture. In the presence
of moisture, decomposes hydrolytically to form brown PbO2. M.p. 175-180°C
(some decomposition); d (17X°C) 2.23. Hydrolyzed by water, forming PbO2 and
acetic acid. Dissolves in hot acetic acid without decomposition; slightly
soluble in dry CHCl3, CCl4 and C6H6.


REFERENCES:

  1) H. F. Walton. Inorganic Preparations, New York 1948, p. 138.
  2) H. S. Booth, Inorg. Syn., Vol. I, New York-London 1939, p. 47.
  3) O. Dimroth and R. Schweizer, Ber. 56, 1375 (1923).

Lead tetraacetate can also be made through electrolysis:

  4) CA 51, 16146 (1957)
  5) CA 74, 49005x (1971)
  6) Oxidations in Org. Chem. part A, Wiberg, 1965, p277-366 - Academic Press.
  7) Pure Appl. Chem. 13, 567-81 (1966)


