Subtle electronic differences between metals in the periodic table can lead to radical changes in chemical reactivity. Now, a research team led by Zhaomin Hou from the RIKEN Advanced Science Institute, Wako, has found that scandium, a seldom-studied rare-earth metal, enables the catalytic addition of functional groups to unsaturated carbon bonds with better selectivity than other metals1—a boon to chemists seeking precise control over molecular assembly.
Hou and his team are experts in the field of rare-earth materials, and recently discovered that a so-called ‘half-sandwich’ complex, comprising a scandium cation and a pentagonal carbon ring, could efficiently catalyze production of long polymer chains.
“Our scandium complex acted as an excellent catalyst for olefin polymerization, with unprecedented activity and selectivity,” says Hou. Because the scandium complex targeted unsaturated carbon bonds during the polymerization process, the researchers realized its enormous potential in other important synthetic reactions, such as carbometalation.
During carbometalation, a metal catalyst helps an organic unit, such as a methyl group, and a metal—commonly aluminum—to add to a carbon–carbon double or triple bond. Researchers can then replace the metal with another molecular group, making carbometalation an effective way to construct carbon-based frameworks containing multiple, branched functional units.
What is difficult, though, is controlling the regioselectivity of the catalytic addition—the precise positions where the organic and metal units add to the unsaturated carbon bonds. When the team first attempted carbometalation with the scandium catalyst and a typical triple-bonded carbon molecule, it achieved only moderate regioselectivity, similar to other transition metal catalysts.
However, when the researchers tethered a silyl ether—a group containing silicon, oxygen, and hydrocarbon atoms—to the end of the triple-bonded carbon substrate, the carbometalation proceeded with extremely high regioselectivity; over 99% of the final product was isolated as a single chemical isomer. Further experiments revealed that the combination of a silyl ether tether group and a scandium-based catalyst enabled controllable carbometalation on numerous unsaturated organic molecules—in many cases, with higher regioselectivity than any other catalyst.
According to Hou, the unprecedented selectivity achievable through this method is due to a balanced interaction between the oxygen atom of the silyl ether adduct and the scandium cation. “This interaction should not be too strong,” he says, “otherwise coordination and insertion processes around unsaturated carbon–carbon triple and double bonds would be hampered.”
The researchers are currently exploring new ways to utilize rare-earth complexes for chemical transformations involving carbon and other elemental bonds.
The corresponding author for this highlight is based at the Organometallic Chemistry Laboratory, RIKEN Advanced Science Institute
Saeko Okada | Research asia research news
Researchers identify potentially druggable mutant p53 proteins that promote cancer growth
09.12.2016 | Cold Spring Harbor Laboratory
Plant-based substance boosts eyelash growth
09.12.2016 | Fraunhofer-Institut für Angewandte Polymerforschung IAP
Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.
Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was...
In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
09.12.2016 | Life Sciences
09.12.2016 | Ecology, The Environment and Conservation
09.12.2016 | Health and Medicine