744
M. BAUDLER
red heat, but simultaneous decomposition of the salt to SnS and
Na s S x occurs.
Readily soluble in water (57.1 g. in 100 g. of solution at 18°C).
Monoclinic crystals.
REFERENCE:
E. E. Jelley. J. Chem. Soc. (London) 1933, 1580.
Tin (IV) Sulfate
Sn(SO4)2-2H8O
The preparation starts from a-stannic and sulfuric acids.
Freshly precipitated a-stannic acid (see p. 737) is dissolved
in an excess of hot, dilute sulfuric acid, and the colorless solution is evaporated. White crystals of Sn(SO^ 3 • 2 HSO separate.
These acquire a needle-shaped, platelike, or prismatic appearance with increasing acid concentration. After cooling, the salt
is suction-filtered through a fritted glass crucible and left for some
times in a desiccator, on clay and over P a O B , in order to free it of
the mother liquor. The pure product must be stored in sealed
ampoules, since it is very hygroscopic.
PROPERTIES:
Formula weight 346.85. Colorless, crystalline substance; very
hygroscopic. Hydrolyzes completely in water, with separation
of a-stannic acid. Readily soluble in dilute sulfuric acid.
REFERENCES:
A. Ditte. Comptes RendusHebd. Seances Acad. Sci. 104_, 172 (1887).
Tetra methyl tin
Sn(CH3)4
The smoothest conversion and the best yields are obtained in
the Grignard reaction whereby SnCL, is treated with a CHgMgBr
solution:
4Mg + 4CH3Br ( e t h . 4 CH3MgBr
97.3
379.8
4 CHsMgBr + SnCl4
260.5
(ether)
Sn(CH3)4 + 4 Mg(CI, Br)2
178.8
13. TIN AND LEAD
745
The Grignard reagent (CH3MgBr) is prepared in a 1-liter,
two-neck flask provided with a reflux condenser and a gas inlet
tube reaching to the bottom. A CaCl 8 drying tube is attached
to the end of the condenser to prevent access of atmospheric
moisture. The flask is charged with 24.5 g. of Mg shavings
(about 1 gram-atom) and 500 ml. of carefully dried ether. The
reaction is initiated with about 1 g. of "activated" Mg turnings.
These are prepared as follows: About 1 g. of Mg turnings and
0.5 g. of I 3 are carefully heated in a dry test tube over a free
flame, until most of the iodine sublimes onto the cool part of
the tube. After cooling in a descicator the turnings, which are
covered with a brownish layer, are placed in the reaction flask.
Pure CH 3 Br from a cylinder or from a cooled supply trap is slowly
added to the liquid via the gas inlet tube. If the conversion to
CH3MgBr does not start within 3 minutes (which can be recognized
by the persistence of the iodine color) then the CH3Br flow is
interrupted and the flask is carefully heated on a water bath to
60 to 70°C. A vessel filled with ice water must be on hand to p e r mit rapid cooling if the reaction is too vigorous. Once the reaction
starts, the addition of CH3Br is so regulated that the ether r e mains at a moderate boil. It is absolutely necessary in further
processing that the Mg be completely dissolved. About 120 g. of
CH3Br (about 1.25 moles) is normally needed to accomplish this,
but considerably more may be if this reagent is introduced too
rapidly. In the latter case, most of the methyl bromide escapes
through the condenser without reacting. If necessary, the last
traces of Mg can be converted by adding about 5 g. of CHgl through
the reflux condenser. After the addition, the reaction mixture is
refluxed for half an hour on the water bath. The flask is then
closed off with a CaCl a tube and allowed to stand at room temperature until further use.
The reaction with SnCla is carried out under a hood, using a
three-neck, 1-liter ground glass flask provided with a reflux
condenser, a well-sealed stirrer and a dropping funnel. Both
the condenser and the dropping funnel are equipped with CaClg
drying tubes. The SnCl4 cannot be added directly to the Grignard
reagent, as is usually done in analogous preparations. This
reaction is too violent since even the reaction of SnCl4 with ether,
which yields a crystalline etherate, is very exothermic. It is
therefore much more practical to prepare this etherate separately
and then add to it the Grignard solution.
The reaction flask is charged with 200 ml. of absolute ether,
and 45 g. of anhydrous SnCl4 (see p. 729) is added dropwise,
while vigorously stirring and cooling with ice water. After the
addition, the dropping funnel is replaced with a clean one and the
ethereal solution of CHgMgBr is added over a period of 45 minutes
with vigorous agitation. That addition proceeds at room temperature.
746
M. BAUDLER
The reaction is completed by refluxing for 2 days (twice for 10
hours) on the water bath. The product is then checked for malodorous methyltin halides which are initially present. If the odor
is present, refluxing must be continued. The reaction mixture is
then carefully decomposed with distilled water from the dropping
funnel. The flask must be cooled with ice water, and addition is
continued until the initial effervescence subsides. Finally, 10%
hydrochloric acid is added until the precipitated Mg salt dissolves
completely and two layers can be observed in the solution (if
necessary, let stand for some time). The ether layer is separated
in a separatory funnel and washed successively with some water
and a 5% KF solution. Any methyltin halides still present are thus
converted to the corresponding fluorides. These are insoluble
and can be filtered off. The ether solution is dried for several
hours with CaCl 3 . Then most of the solvent is removed in a
slow distillation with a suitable column. The remainder is fractionated at atmospheric pressure, using the same column. The
boiling point of the pure substance is 76°C. The yield corresponds to about 90% of theoretical, based on the SnCl4 used.
PROPERTIES:
Water-clear, highly refractive, mobile liquid with an agreeable,
sweet, ether odor; poisonous; stable to air and water. B.p. 76°C,
df5 1.291. Insoluble in water; miscible in all proportions with
ether, absolute alcohol and other organic solvents.
REFERENCES:
F. Ossenbrink. Thesis, Cologne, 1952; see Also E. Krause and
A. von Grosse. Die Chemie der metall-organischen Verbindungen, Berlin, 1937, p. 314 ff.
Tetraethyltin
Sn(C2H5)4
4 C 2 H 5 Br + 4 Mg = 4 C 2 H 5 MgBr
435.9
97.3
4C 2 H 5 MgBr + SnCl4 = Sn(C2H5)4 + 4Mg(Cl, Br)2
260.5
234.9
The preparation is analogous to that of Sn(CI^)4. The reader
is referred to the detailed description of the procedure given
under that compound, unless changes are expressly indicated in
what follows.
13. TIN AND LEAD
747
An identical two-neck flask is used for the preparation of the
C3HsMgBr solution. However the second neck carries a dropping
funnel for the addition of CaHgBr instead of a gas inlet tube. About
136 g. of C3HgBr is needed for the conversion of 24.5 g. of Mg
shavings.
Anhydrous SnCl4 (45 g.; see p. 729) is carefully added dropwise to the absolute ether solution of C3HgMgBr in the apparatus
previously described for the further reaction. This addition must
be done under a hood. The reaction flask is cooled with flowing
water. With larger charges the preparation of the SnCl4 etherates
should be carried out separately and the Grignard solution should
then be added dropwise. After completion of the addition, the mixture is refluxed for one hour and the ether is then completely distilled off on a water bath. The residue is heated for 1/2 hour on
a boiling water bath and after cooling is remixed with the ether
previously removed. Finally, with the reflux condenser in place,
water and 5% hydrochloric acid are carefully added from the
dropping funnel until a clear separation of the layers is observed.
The ether solution is then processed in the same way as Sn(CHg)4.
Because of its high boiling point, the last fractionation of the very
concentrated product is carried out under aspirator vacuum.
Boiling point of the pure substance (13 mm.) is 78°C.
The yield is approximately 75%.
PROPERTIES:
Colorless, highly refractive, mobile liquid with an agreeable,
sweet, ether odor; poisonous; stable to air and water; quite
flammable.
M.p -112°C, b.p. 175°C; d| 5 1.192.
Insoluble in water; miscible in all proportions with ether, absolute alcohol and other organic solvents.
REFERENCES:
E. Krause and A. von Grosse. Die Chemie der metall-organischen
Verbindungen [The Chemistry of Organometallic Compounds]
Berlin, 1937, p. 314 ff.;
F. Ossenbrink. Thesis, Cologne, 1952.
Tin (IV) Acetate
Sn(CH3COO)4
Snl4 + 4 TICH3COO = Sn(CH3COO)4 + 4 Til
626.4
1057.7
354.9
1329.2
The reaction of TICH3COO with Snl4 requires exclusion of moisture. It proceeds in a 150-ml. three-neck ground glass flask