Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Metal Strengthens Double Bond

10.12.2012
Professor Holger Braunschweig and his team come up with stunning new discoveries in chemistry with great regularity. This time, the Würzburg researchers turn an established model describing catalytic processes on its head.

Be it margarine, chemical fertilizers or plastic cups: The chemical principle of catalysis plays an important role in the production of various products. In the production process, a so-called catalyst enables certain reactions to proceed. Catalysts are indispensable for hardening vegetable oils into margarine or for producing polyethylene and other plastics.

Take the example of margarine: In order to create spreadable fat from liquid vegetable oil, you need to break bonds in hydrogen molecules. This is where a metallic catalyst comes in. Its metal atom pushes electrons into the bonds, destabilizing them in the process, so that they are ready for the desired reaction.

Established model turned on its head

A metal donates electrons, thereby weakening chemical bonds: This effect – known as the "Dewar-Chatt-Duncanson model" – has been known to chemists since 1953. However, the model must now be supplemented, having been turned on its head by chemists of the University of Würzburg.

The new insight: The electrons of a metal can also strengthen a chemical bond – at least in the case of a double bond between two boron atoms. This is reported in the journal "Nature Chemistry" by researchers of Professor Holger Braunschweig's study group.

Theory experimentally confirmed

A double bond between two boron atoms can accommodate exactly two additional electrons. Chemists speak in this context of a "free II-orbital". If you fill this space, the bond should become stronger: This is the assumption that the Würzburg chemists Dr. Rian Dewhurst and Dr. Alfredo Vargas started from. They modeled their idea on the computer and found it confirmed – purely theoretically at first.

The next step was to confirm the theory by means of an experiment. Within the study group, the researchers found a molecule that was ideally suited for this purpose: a so-called platinum diboranyl complex. This molecule had been synthesized in a sophisticated process by Alexander Damme when working on his doctoral thesis.

Boron-boron double bond plus platinum

The centerpiece of the complex consists of two boron atoms that are linked to each other by a single bond in close proximity to a platinum atom. Damme devised the following procedure: He forced additional electrons on the complex, thus producing a boron-boron double bond.

According to the established model, this double bond should have been weaker than a "normal" boron-boron double bond due to the influence of the platinum metal. In actual fact, however, the bond even proved to be stronger. This was shown in a single crystal X-ray diffraction analysis of the material. This method allows you to determine how far the atoms of a molecule are apart from each other. The closer they are together, the stronger their bond will be. The Würzburg chemists found out that two boron atoms in a double bond come significantly closer together in the presence of platinum than they do without the metal.

New knowledge for textbooks

What are the consequences of this discovery? The everyday practice in chemical laboratories and industrial processes won't be affected for now. But the chemistry textbooks need to be supplemented. To be sure, the "Dewar-Chatt-Duncanson model" has not yet become obsolete; it remains applicable to carbon compounds. But it needs to be substantially extended now. You never know – maybe a model by the name of "Braunschweig-Damme-Dewhurst-Vargas" will be added.

“Bond-strengthening II backdonation in a transition-metal II-diborene complex”, Holger Braunschweig, Alexander Damme, Rian D. Dewhurst, and Alfredo Vargas, Nature Chemistry, 2012 Dec 9, DOI: 10.1038/NCHEM.1520

Contact person

Prof. Dr. Holger Braunschweig, Institute for Inorganic Chemistry of the University of Würzburg, T +49 (0)931 31-85260, h.braunschweig@uni-wuerzburg.de

Robert Emmerich | Uni W¨¹rzburg
Further information:
http://www.uni-wuerzburg.de

More articles from Life Sciences:

nachricht One step closer to reality
20.04.2018 | Max-Planck-Institut für Entwicklungsbiologie

nachricht The dark side of cichlid fish: from cannibal to caregiver
20.04.2018 | Veterinärmedizinische Universität Wien

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Spider silk key to new bone-fixing composite

University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.

Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.

Im Focus: Writing and deleting magnets with lasers

Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...

Im Focus: Gamma-ray flashes from plasma filaments

Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.

The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...

Im Focus: Basel researchers succeed in cultivating cartilage from stem cells

Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.

Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...

Im Focus: Like a wedge in a hinge

Researchers lay groundwork to tailor drugs for new targets in cancer therapy

In the fight against cancer, scientists are developing new drugs to hit tumor cells at so far unused weak points. Such a “sore spot” is the protein complex...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

IWOLIA: A conference bringing together German Industrie 4.0 and French Industrie du Futur

09.04.2018 | Event News

 
Latest News

Magnetic nano-imaging on a table top

20.04.2018 | Physics and Astronomy

Start of work for the world's largest electric truck

20.04.2018 | Interdisciplinary Research

Atoms may hum a tune from grand cosmic symphony

20.04.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>