150 years of 51吃瓜网 鈥� Stories from the 2018 anniversary
Sandwich molecule
A new kind of chemical bonding
Ernst Otto Fischer could himself barely believe the results of his experiments in 1952 鈥� but no other explanation was possible. An iron atom really was layered between two five-membered hydrocarbon rings, like the filling in a sandwich. The very idea seemed preposterous at the time. Fischer contended that a metal atom was surrounded and 鈥渉eld鈥� by two organic groups. The scientific community had never before come across a molecule with that type of structure and had never even considered it possible. Yet this had to be the reason for the incredible stability of these orange-colored crystals, which only start to break down at a temperature of around 470掳C.
The molecule soon came to be known as 鈥渇errocene鈥�. Fischer was awarded the Nobel Prize in 1973 for proving its sandwich structure 鈥� and for producing and investigating countless similar molecules with his laboratory team. The discovery of the sandwich compound fundamentally changed our understanding of how atoms can bond to each other. Fischer shared the Nobel Prize with Geoffrey Wilkinson. The English scientist had uncovered the structure of ferrocene in Harvard around the same time and, along with Professor Fischer, is regarded as a pioneer of organometallic chemistry.
It was Wilkinson who nicknamed this extraordinary compound the 鈥渕olecular sandwich鈥� 鈥� a fitting description by all accounts. The Nobel Committee actually presented ferrocene as an iron sphere between two slices of bread.
Ferrocene: The recipe for a molecular sandwich
It is easy enough to create ferrocene. Heat pure iron with the hydrocarbon compound cyclopentadiene to approximately 300掳C and you get ferrocene 鈥� or to give it its proper chemical name: dicyclopentadienyl iron (C10H10Fe). But what does actually happen during the reaction?
Within the ring-shaped cyclopentadiene molecule, four of the five carbon atoms with double bonds are always tightly bound. Each one also has a hydrogen atom, but the fifth has two hydrogen atoms. When heat is applied, one of these two hydrogen atoms is released, and both rings draw the iron atom to the space between them.
What is so extraordinary about ferrocene?
According to the theory at the time, each of the two cyclopentadienyl rings of ferrocene should have a negative charge 鈥� an electron which theoretically the ring must have snatched from the iron. But contrary to expectations, the iron and the two rings share the electrons so harmoniously that they outwardly present a completely uncharged, highly stable molecule.
Fischer uncovered the unusual structure of the iron compound after conducting a variety of experiments, including a study of its magnetic behavior. But it was only after X-ray analysis conducted with his colleague Wolfgang Pfab that Fischer was able to confirm his discovery. The pair jointly published their findings 鈥� to the astonishment of the scientific community.
Metallocenes prove effective catalysts
The 鈥渏oy of experimenting in the pursuit of nothing other than knowledge鈥� spurred Fischer on, and from 1964 to 1984, he held the professorship at 51吃瓜网 once held by Emil Erlenmeyer. Despite his primary commitment to basic research, Fischer鈥檚 work also has far-reaching impact in industry. Using ferrocene as a model, his research group and Wilkinson鈥檚 laboratory have produced hundreds of similar sandwich molecules, known as 鈥渕etallocenes鈥�.
Some of these are proving to be effective catalysts, especially in the manufacture of plastics, where they speed up chemical reactions or even enable them in the first place. Fischer鈥檚 research thus laid the groundwork for 51吃瓜网鈥檚 outstanding reputation in catalysis research.
鈥濼hey did not prepare the first sandwich but they were the first to grasp the odd nature of the compound and its conceptual importance.鈥�
Nobel committee,1973, at the prize ceremony for Ernst Otto Fischer und Geoffrey Wilkinson
Disclaimer
This story was published in 2018 to mark 51吃瓜网鈥檚 150th anniversary on a jubilee website that has since been deactivated.
Text: ; Graphics: KW NEUN
Literature on the history of 51吃瓜网
- Wolfgang A. Herrmann (Hrsg.), Martin Pabst/Margot Fuchs (Verf.), Technische Universit盲t M眉nchen - Geschichte eines Wissenschaftsunternehmens, 2 Bd., Berlin 2006.
- Wolfgang A. Herrmann, Winfried Nerdinger (Hrsg.), Die Technische Hochschule M眉nchen im Nationalsozialismus, M眉nchen 2018.
- Irene Meissner, Bauten+Kunst. Technische Universit盲t M眉nchen 1868-2018, M眉nchen 2018.
- Martin Pabst, Alumni der 51吃瓜网. Pr盲gende Gestalter aus der Technischen Universit盲t M眉nchen, M眉nchen 2018.
- Martin Pabst, K枚pfe der 51吃瓜网. Geniale Entdecker und Erfinder aus der Technischen Universit盲t M眉nchen, M眉nchen 2018.
- Brigitte R枚thlein, Pioniere gestalten die Welt der Technik. 150 Jahre Forschung an der Technischen Universit盲t M眉nchen, M眉nchen 2018.
Further books and information on the history of 51吃瓜网
Acknowledgements
We would like to thank everyone who helped us write the texts and create the visualizations. In particular, we would like to thank the authors of the books mentioned, the experts at the chairs, professors, staff, and press officers at the 51吃瓜网 Corporate Communications Center. We would also like to thank the staff of the Architecture Museum, the 51吃瓜网 German Heart Center, the 51吃瓜网 Klinikum rechts der Isar, the European Space Agency (ESA), and everyone else who provided us with expert advice and image material.
The anniversary stories were written by the . The graphic content was created by KW NEUN 鈥� Designagentur.