Organic Syntheses, Coll. Vol. 4, p.473 (1963); Vol. 36, p.31 (1956).
[I. METALLIC SODIUM METHOD]
In a 250-ml. three-necked flask
, fitted with a mechanical stirrer
, a reflux condenser
, and an inlet for admission of nitrogen
, is placed 100 ml. of tetrahydrofuran (Note 1)
. With stirring, 27.1 g. (0.166 mole) of anhydrous ferric chloride
is added in portions, followed by 4.7 g. (0.084 g. atom) of iron powder (Note 2)
. The mixture is heated with stirring under nitrogen
at the reflux temperature for 4.5 hours, giving a gray powder with a brown supernatant liquid.
During this time, a second system is assembled, consisting of a 500-ml. three-necked flask
fitted with a mechanical stirrer, a reflux condenser topped with a calcium chloride-filled drying tube
attached to a xylene-filled bubbler
, and a pressure-equalizing dropping funnel
through which a slow stream of nitrogen
is passed into the flask. In the flask are placed 200 ml. of sodium-dried xylene
and 11.5 g. (0.5 g. atom) of sodium
. The mixture is heated to boiling, and the sodium
is finely dispersed by rapid stirring (Note 3)
. Stirring is continued while the mixture is allowed to cool in a nitrogen
atmosphere. The cooled mixture is allowed to settle, and the bulk of the xylene
is siphoned. Tetrahydrofuran (200 ml.) (Note 1)
is added through the separatory funnel
, and to the stirred mixture, cooled in ice, is added 42 ml. (0.5 mole) of cyclopentadiene (Note 4)
in portions during 1 hour (Note 5)
. Stirring is continued for 2–3 hours in the cold, after which only a small amount of sodium
The cooled contents of the 250-ml. flask containing ferrous chloride (Note 6)
are added to the cold sodium cyclopentadienide
solution while passing a stream of nitrogen
through both flasks. The combined mixture is stirred for 1.25 hours at a temperature just below reflux. Solvent is removed by distillation, and the ferrocene
is extracted from the residue with several portions of refluxing petroleum ether
). The product is obtained by evaporation of the petroleum ether
may be purified by recrystallization from pentane
, and methanol
have also been used) or by sublimation. The yield is 31–34 g.
) (Note 7)
, m.p. 173–174°.
The quality of the iron
used in preparing the ferrous chloride
has a marked effect on the yield of ferrocene
. The checkers employed Rascher and Betzold (730 N. Franklin, Chicago, Ill.) 300-mesh iron powder
, reduced by hydrogen
. When 40-mesh iron filings
were used, the yield of ferrocene
was much lower (ca. 33%).
The checkers employed a "Mixmaster"-type motor and a Hershberg stirrer
made from tantalum wire
, b.p. 40°
, is obtained by heating commercial 85% dicyclopentadiene (e.g., from Matheson, Coleman and Bell Company, Norwood, Ohio)
under a short column ( in. diameter × 8–12 in. length) filled with glass helices
. The distilled cyclopentadiene
is collected in a receiver
which is maintained at Dry Ice temperature until the cyclopentadiene
is used. Methylcyclopentadiene
and other substituted cyclopentadienes such as indene
may also be employed for the synthesis of the correspondingly substituted ferrocenes. In these cases, the reaction of the hydrocarbon with sodium
is much slower than with cyclopentadiene
, and refluxing for several hours is required to complete the reaction.
The submitter reported yields up to 90%
by this method.
[II. DIETHYLAMINE METHOD]
The conditions given in the preceding preparation are used for obtaining a suspension of 0.25 mole of ferrous chloride in 100 ml. of tetrahydrofuran (Note 1)
, contained in a 250-ml. flask. The tetrahydrofuran
is then removed under reduced pressure until the residue is almost dry. The flask is cooled in an ice bath
, and to the residue is added a mixture of 42 ml. (0.5 mole) of cyclopentadiene
and approximately 100 ml. (about 1 mole) of diethylamine
. The mixture is stirred vigorously at room temperature for 6–8 hours or, conveniently, overnight. The excess amine is removed under reduced pressure, and the residue is extracted repeatedly with refluxing petroleum ether
. The extract is filtered hot, and the solvent is evaporated to leave ferrocene. The product is purified by recrystallization from pentane
or by sublimation. The yield is 34–39 g.
), m.p. 173–174°.
All precautions with regard to the purification of tetrahydrofuran
, the quality of the iron powder
, the rapid stirring, the maintenance of a nitrogen
atmosphere, and the handling of cyclopentadiene
, described in the preceding preparation, are followed.
This preparation is referenced from:
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