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CHEM3119 Materials Chemistry

Generic skills plus

PROJECT E: Ferrocene


EXPERIMENT E1: PREPARATION OF FERROCENE AND A DERIVATIVE
EXPERIMENT E2: SPECTROSCOPIC STUDIES OF FERROCENE AND ACETYLFERROCENE
EXPERIMENT E3: FURTHER INVESTIGATIONS OF FERROCENE

Introduction
Organometallic chemistry has developed into a major branch of inorganic chemistry. Defined as
the chemistry of the metal-carbon bond, its area of interest extends from various aspects of valence
theory to chemical technology, from bonding in metal π-complexes, for example, to the catalytic
synthesis of industrial alcohols and aldehydes.
Organometallic chemistry owes much of its present status to the discovery of ferrocene (Ref. 1) in
1951 and to work done subsequently on the chemistry of cyclopentadienyl compounds (Ref.2).
Since the preparation of ferrocene involves a number of techniques typical of organometallic
chemistry it is practically and historically an appropriate synthesis for senior chemistry students to
undertake.

Experimental Method
Before commencing this experiment, you must complete a HIRAC form and submit it to a
Demonstrator, along with your Name/SID, to be assessed. Your HIRAC marks will be
entered into the system. You may get your HIRAC assessed on any day prior to the
session/experiment that you are about to start.

CAUTION: Cyclopentadiene exists in equilibrium with its dimer. The equilibrium strongly
favours the dimer at and above room temperature. Cyclopentadiene is therefore stored in the
freezer in the service room.

Both ferrocene and acetylferrocene, however, are air and water-stable solids at room temperature.

i. Synthesis of Ferrocene, (η5-C5H5)2Fe, di-η5-cyclopentadienyliron.
Obtain the kit for this preparation from the appropriate bench (lab 439, check WHEREIS list). Make
sure that the apparatus is clean and dry. The Ferrocene workstations have been set up for you in the
fume hoods near the instrument rooms, lab 439. Workstations consist of hotplate stirrer (although
heating is not required), nitrogen line with an adaptor and the bubbler line. Please make sure that
the workstations remain intact after use; reassemble all apparatus and wipe any spills from the
hotplate stirrer and the adaptors. Clean the glassware and return your kit to its designated location.
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Figure 1. Experimental Setup for Ferrocene Synthesis



Add 25 g of powder potassium hydroxide using a powder funnel. Set up the apparatus shown above
in Figure 1. Place the magnetic stirrer bar in the flask, attach dropping funnel, nitrogen and bubbler
lines. Flush the system with nitrogen for a few minutes before adding the reagents. Add 60 mL of
1,2-dimethoxyethane to the flask through the middle neck and commence stirring. Reattach the
dropping funnel and flush the system with nitrogen for another 10 min. The flow of nitrogen should
be adjusted so that a steady flow passes through to the bubbler.

CAUTION: See a demonstrator before you use the nitrogen.


Obtain iron(II) chloride tetrahydrate (FeCl2·4H2O) from the desiccator. Iron(II) chloride should be
green-yellow in colour, if it is more like orange it has oxidised into iron(III) chloride and should
not be used. Make sure that exposure of Iron(II) chloride to the air is reduced to a minimum. Use
6.5 g of Iron(II) chloride. Crush any lumps and very quickly dissolve in 25 mL of dimethylsulfoxide
(DMSO). Ensure that dropping funnel’s tap is closed. Transfer the solution of Iron(II) chloride
in DMSO to the dropping funnel and stopper the funnel. Do not add the solution to the flask at this
stage.
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Obtain 6 mL of freshly distilled cyclopentadiene from the service room. Keep this on ice during
collection and addition. Remove the nitrogen line going to the bubbler and (with the nitrogen still
flowing) add 5.5 mL of cyclopentadiene dropwise from a Pasteur pipette. Replace the adaptor to
the nitrogen bubbler and stir the mixture vigorously. The empty cyclopentadiene vial should be
capped and placed in the broken glass bin.
Do not wait for too long before adding the next reagent. The solution will warm up and
the cyclopentadiene will polymerise.