Experiment 1
Synthesis, Purification, and Characterization of
Ferrocene
Part A:
Part B:
Part C:
Synthesis of Ferrocene
Purification of Ferrocene
Characterization of Ferrocene
Introduction The compound ferrocene, or also known as
[Bis(cyclopentadienyl)iron(II)], is prepared via the direct reaction
of potassium hydroxide, cyclopentadiene, and iron (II) chloride
tetrahydrate.
8 KOH + 2 C5H6 + FeCl2 * 4 H2O  Fe(C5H5)2 + 2KCl + 6 KOH*H2O
Total time required: 1 day (or 5 hours if product dried in vacuo)
Actual working time: 4 hours
Preliminary reading and techniques assignment:
J. Birmingham, “Synthesis of Cyclopentadiene Metal
Compounds,” Adv. Organometallic Chem., 2, 365 (1965); G. E.
Coates, M. L. H. Green, and K. Wade, Organometallic
Compounds, vol. 2, Methuen & Co. Ltd., London, 1968, pp. 90115; W. L. Jolly, Inorg. Chem., 6, 1435 (1967); and, W. L. Jolly,
“The Synthesis and Characterization of Inorganic Compounds,”
Chapter 5, Solvents, and Appendix 4, Compressed Gas Cylinders.
Reagents Required:
11 ml of 1,2-dimethoxyethane
About 5.2 g of KOH pellets (protected from moisture)
1 ml of cyclopentadiene – obtained from the thermal
cracking of 2 ml dicylopentadiene
(3a,4,7,7a-tetrahydro-4,7-methanoindene)
1.1 g of FeCl2 * 4 H2O
5 ml of dimethyl sulfoxide (DMSO)
5 ml of aqueous HCl
About 20 g of ice
Cylinder of nitrogen or argon
Experimental Section
Part A:
Synthesis of Ferrocene
Safety Recommendations
(1) Potassium Hydroxide (CAS No. 1310-58-3): Poison!
Danger! Corrosive. Causes severe burns to skin,
Eyes, respiratory tract, and gastrointestinal tract.
Material is extremely destructive to all body tissues.
May be fatal if swallowed. Harmful is inhaled.
(Refer to attached MSDS forms for further info)
(2) Hydrochloric Acid (CAS No. 7647-01-0):
Poison! Danger! Corrosive. Liquid and mist cause
severe burns to all body tissue. May be fatal is
swallowed or inhaled. Inhalation may cause lung
damage.
(Refer to attached MSDS forms for further info)
(3) Dimethyl Sulfoxide (CAS No. 67-68-5): Warning!
Harmful if swallowed, inhaled or absorbed through
the skin. Causes irritation to skin, eyes, and
respiratory tract. Combustible liquid and vapor.
(Refer to attached MSDS forms for further info)
(4) Dicyclopentadiene (CAS No. 77-73-6): May cause
mild eye irritation, severe skin irritation, and is
toxic if inhaled or ingested. Keep away from heat,
sparks, and flames.
(Refer to attached MSDS forms for further info)
(5) Dimethoxyethane (CAS No. 110-71-4): Warning!
Flammable liquid and vapor. Affects central
nervous system. May affect blood and blood
forming organs, reproductive system, liver and
kidneys. May form explosive peroxides in air.
Possible birth defect hazard. May cause birth
defects based on animal data. May be harmful if
absorbed through skin. May cause to eyes and
respiratory tract.
(Refer to attached MSDS forms for further info)
(6) Iron (II) chloride tetrahydrate
(CAS No. 13478-10-9): Danger! Corrosive.
Causes severe irritation or burns to every area of
contact. Harmful if swallowed or inhaled. Affects
the liver.
(Refer to attached MSDS forms for further info)
(7) Cyclopentadiene (CAS No. 542-92-7): May cause eye
irritation. May cause coughing and sore throat if
inhaled. Flammable, keep away from heat, sparks,
and flames. Above 25 explosive vapor/air
mixtures may be formed.
(Refer to attached MSDS forms for further info)
Chemical Data
Compound
1
2
3
4
5
6
7
FW
56.11
36.46
78.13
132.20
90.12
198.812
66.0
Amount
5.2 g
7.8 g
4.35 ml
3 ml
10.4 ml
1.1 g
1 ml
mol
0.09
0.21
0.06
0.02
0.12
0.01
0.02
mp (C)
406
-114.18
19
-58
105
-85
bp (C)
1327
-85
189
172
82-83
1023
41.5-42
Density
2.044
1.600
1.1014
0.96
0.86
1.93
0.8
Required Equipment
Fractional distillation apparatus
30 ml three-necked (standard taper joints) round bottomed flask
Magnetic stirrer and large stirring bar
T-tube mercury bubbler with standard-taper connection to flask
Pyrex Petri dish with cover, 150 x 20 mm
Experimental Procedure
The potassium hydroxide pellets are ground with a mortar and
pestle until the particles are less than 0.5 mm in diameter. Make
sure that the potassium hydroxide has minimal exposure to the
atmosphere, and stored in a tightly capped bottle.
The cyclopentadiene is made from the thermal cracking of
dicyclopentadiene. The dicyclopentadiene is slowly distilled in the
hood through a fractionating column, collecting only the material
that refluxes below 44. (See Figure 4.2)
After putting on some gloves, the magnetic stir bar, 11 ml of 1,2dimethoxyethane, and 5.2 g of the powdered potassium hydroxide
are placed in the three-necked flask. (See Figure 32.12) One side
neck is stoppered and the other is connected to the t-tube mercury
bubbler and the nitrogen cylinder. While this mixture is slowly
stirring, and being flushed by the stream of nitrogen, 1.0 ml of
cyclopentadiene is added. The center neck is then fitted with the
dropping funnel with its stopcock open. After about 99% of the air
has been flushed from the flask, the stopcock is closed, and the
solution of 1.1 g of FeCl2 * 4 H2O in 5 ml of DMSO is placed in
the drop funnel. The mixture is stirred vigorously. After 10
minutes has passed, the t-tube is lifted above the level of mercury
(to reduce pressure to atmospheric), and drop-by-drop addition of
the iron(II) chloride solution is begun. The rate should be adjusted
so that the entire amount is added in 45 min.
After the complete addition, the stopcock is closed and vigorous
stirring is continued for 30 min. Finally the nitrogen flow is
stopped, and the mixture is added to 5 ml of 6 M HCl and about 20
g of crushed ice. The resulting slurry is stirred for about 15 min,
and the precipitate is collected on a sintered-glass funnel and
washed with four 3.0 ml portions of water. The moist solid is
spread out on a large watch glass and dried in the air overnight.
The yield is approximately 1 g of ferrocene.
Chemical Data
Compound
Ferrocene
FW
Amount
186.04 1 g
Part B:
mol
0.005
mp(C)
173-174
bp(C)
249
Density
-
Purification of Ferrocene
An extremely pure product can be obtained by sublimation. The
material to be sublimed is placed in an inverted cover of a Petri
dish, making sure that none of the material is within 2 mm of the
sidewall of the cover. The Petri dish itself (the smaller of the two
pieces) is inverted and placed in the cover, and then the entire unit
is placed on a hot plate. The hot plate is slowly warmed up until
the surface of the unit is almost too hot to touch. After 4 to 10
hours, the ferrocene should be completely sublimed onto the upper
glass surface and should be completely separated from the bottom
residue layer. The yield is now approximately 0.9 g. (see Figure
32.13)
Part C:
Characterization of Ferrocene
The infrared spectrum of ferrocene may be determined using a KBr
pellet. Absorption bands are observed at the following frequencies
(in cm-1):
170(m), 478(s), 492(s), 782(w), 811(s), 834(w), 1002(s),
1051(w), 1108(s), 1188(w), 1411(s), 1620(m), 1650(m),
1684(m), 1720(m), 1758(m), 3085(s)
The ultra violet spectrum in ethanol show a maxima at 325 m
(=50) and 440 m (=87) and rising short wavelength absorption
(=5250 at 225 m)
Another determination can be acquired through its melting point
determination, melting at 173-174.
References
1.
2.
3.
J. Birmingham, “Synthesis of Cyclopentadiene Metal
Compounds,” Adv. Organometallic Chem., 2, 365 (1965)
G. E. Coates, M. L. H. Green, and K. Wade, Organometallic
Compounds, vol. 2, Methuen & Co. Ltd., London, 1968, pp. 90115
W. L. Jolly, Inorg. Chem., 6, 1435 (1967)
General References
1.
W. L. Jolly, “The Synthesis and Characterization of Inorganic
Compounds,” Chapter 5, Solvents, and Appendix 4, Compressed
Gas Cylinders.