Ernst Otto Fischer Researcher organometallic Compounds | Alkylidene Alkylidyne Discoverer

Ernst Otto Fischer – researcher of sandwich compounds

Category : Personalities
Published by : Data Research Analyst, Worldofchemicals.com

Biography & contributions

Ernst Otto Fischer, a German chemist and Nobel laureate born on November 10, 1918 – died on July 23, 2007. Fischer carried out research work on synthetic compounds of organic substances and metals. Fischer and British chemist Geoffrey Wilkinson were awarded the 1973 Nobel Prize in chemistry for their independent work on the chemistry of organometallic or sandwich compounds.

Fischer was the first person who predicted the structure of ‘Ferrocene’ synthetic compound and along with that he also given important lectures on

Organometallic compounds

Organometallic chemistry is the study of chemical compounds containing bonds between carbon and a metal. It is the combination of inorganic chemistry and organic chemistry. Organometallic compounds can be used in stoichiometric and catalytic processes, in the production of polyethylene and polypropylene.

Examples of organometallics

Facts about Ferrocene

Ferrocene was accidently discovered in 1951 at Duquesne University in Pittsburgh, Pennsylvania by T.J. Kealy and P.L.Paulson and before Paulson its existence was discovered by Fischer

Preparation

Cyclopentadienyl magnesium bromide (CpMgBr) was reacted with iron (II) chloride in attempt to create a fulvalene. When an orange complex formed instead, the chemists hypothesized that the iron was bound to one carbon in each ring.


Ferrocene’s cyclopentadienyl rings are aromatic – each containing 6 delocalized π electrons like benzene.

Laboratory preparation of ferrocene

Cyclopentadiene undergoes a 4+2 cycloaddition to form dicyclopentadiene. For this reason, cyclopentadiene is usually purified before use. Dicyclopentadiene boils at 170°C and cyclopentadiene boils at 42.5°C. For efficiency, the dicyclopentadiene dimer is thermally cracked using a fractional distillation apparatus. KOH should be grind in a mortar and quickly transfer it to a tared vial.

KOH is hygroscopic and should be ground in small portions (2 g).KOH chemical need to be in dry state. The finely grounded FeCl2.4H2O will also go into solution more effectively. It is then placed in a tared vial. The pre-weighed KOH (15 g) is placed in a 100 mL (14/20) three-neck round bottom flask equipped with a magnetic stirring bar.

1,2-Dimethoxyethane (30 mL) is added with stirring to the KOH. One side of the neck is stoppered and the other is connected to a vacuum line through a gas adapter. While the mixture is slowly stirred and the flask is being purged with a stream of nitrogen, then 2.75 mL amount of cyclopentadiene is added. The resulting solution which is formed is in rose color.

The main neck is then fitted with a pressure equalizing dropping funnel which is labeled as 25 mL with its stopcock open. After fitting of stopcock to the flask second neck round bottom flask that is fitted with a septum,FeCl2.4H2O (3.25 g) and DMSO (12.5 mL) are stirred under a nitrogen atmosphere to dissolve the FeCl2.4H2O

By finishing above procedure, next step should start after about five minutes. The stopcock is closed and then FeCl2 solution is added to the pressure equalizing dropping funnel. The reaction mixture in the three-neck flask is stirred vigorously and the purging with nitrogen is continued. After about ten minutes, the stopper is placed on the dropping funnel, the nitrogen flow is reduced and drop-by-drop addition of the FeCl2 solution is begun.The rate of addition is adjusted so that the entire solution is added in 30 minutes.

Then the dropping funnel stopcock is closed and vigorous stirring of the dark green solution is continued for an additional 30 minutes. Finally, the nitrogen flow is stopped and the mixture is added to a mixture of 45 mL 6M HCl and 50g of crushed ice. Some of the resulting slurry may be used to rinse the reaction flask to maximize the product yield. The slurry is stirred for about 15 minutes and the orange precipitate is collected on a Buchner or Hirsch funnel and washed with four 5-mL portions of water.

The moist solid is spread out on a large watch glass and dried in the air. The compound is then purified through sublimation in a large glass petri dish that is placed on a warm hot plate (100°C). Certain precautionary precedures are required to avoid charring the ferrocene. The purified ferrocene is then characterized by melting point determination, UV-Vis and IR spectroscopies, and cyclic voltammetry.

Applications

It is used as a catalyst for the production of carbon nanotubes

Ferrocene’s derivatives are antiknock agents and also used as fuel for petrol engines.

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Reference

[1] © From, http://imr.chem.binghamton.edu/labs/ferrocene/ferrocene.html