Nav: Home

Facile hydrolysis of the Metal-NHC framework under regular reaction conditions

December 17, 2015

Scientists are involved in a non-stop search of an ideal catalyst, which could facilitate discovery of new reactions, as well as make known reactions more selective, environmentally friendly and economically efficient. Introduction of N-heterocyclic carbene ligands (NHC) made a real breakthrough in the catalysts' development. In combination with transition metal, M/NHC complexes are ubiquitously utilized for developing catalytic applications in modern chemistry.

NHC complexes of transition metals are considered quite suitable for this role, as they possess unique characteristics: high activity, flexibility, tunability, outstanding diversity, and many other unique characteristics. The only "little" problem remains: failure to recycle and re-use metal/NHC complexes. Indeed, these fantastic catalysts are typically of single use and in most cases cannot be isolated back after the reaction. Since metal complexes with NHC ligands are usually considered stable, failure to recycle has been disappointing for researchers for many years.

An unusual finding was reported by the group of researchers led by Prof. Ananikov, who noticed that Ni-NHC complexes do undergo a hydrolysis with a breakage of metal-ligand bond. Depending on the nature of the NHC ligand, noticeable decomposition takes place in the time period from minutes to hours. In some cases the complexes were even sensitive to a trace amount of water and the yield of the reaction depended on the degree of dryness of the reagents and solvents. This phenomenon prompted a question about the moisture resistance of the Ni/NHC complexes, which forced the researchers to re-think the routinely assumed picture.

The study demonstrated that the Ni/NHC complexes can either survive in aqueous solutions during the prolonged time (more than a week) or, in contrast, "live" for a couple of minutes depending on the nature of the carbene moiety. Detailed comparison of the processes showed that complexes decompose into initial reagent and nickel hydroxide. The observed speed of hydrolysis for triazolium complexes is much higher than that for imidazolium or benzimidazolium complexes.

Since water is a common contaminant in regular chemical transformations, the described phenomenon makes an impact on the catalyst' development area Moreover, the observed degradation process may shed some light on the problem of catalyst stability and recycling.
-end-
The article «Facile Hydrolysis of Nickel(II) Complexes with N-Heterocyclic Carbene Ligands» by Alexander V. Astakhov, Oleg V. Khazipov, Evgeniya S. Degtyareva, Victor N. Khrustalev, Victor M. Chernyshev, and Valentine P. Ananikov was published in Organometallics journal published by American Chemical Society.

Reference: Organometallics 2015; DOI: 10.1021/acs.organomet.5b00856

On-line link: http://dx.doi.org/10.1021/acs.organomet.5b00856

Institute of Organic Chemistry, Russian Academy of Sciences

Related Catalyst Articles:

New efficient, low-temperature catalyst for hydrogen production
Scientists have developed a new low-temperature catalyst for producing high-purity hydrogen gas while simultaneously using up carbon monoxide (CO).
Multifunctional catalyst for poison-resistant hydrogen fuel cells
A Kyushu University-led collaboration developed a catalyst that can oxidize both hydrogen and carbon monoxide in fuel cells.
UK Chemistry researchers develop catalyst that mimics the z-scheme of photosynthesis
Published in Applied Catalysis B: Environmental, the study demonstrates a process with great potential for developing technologies for reducing CO2 levels.
New catalyst paves way for carbon neutral fuel
Australian scientists have paved the way for carbon neutral fuel with the development of a new efficient catalyst that converts carbon dioxide (CO2) from the air into synthetic natural gas in a 'clean' process using solar energy.
A rhodium-based catalyst for making organosilicon using less precious metal
Researchers at Tokyo Institute of Technology have reported a new catalyst composed of silica, a rhodium complex and tertiary amines(term1) that significantly boosts hydrosilylation reactions.
Splitting carbon dioxide using low-cost catalyst materials
EPFL scientists have built the first Earth-abundant and low-cost catalytic system for splitting CO2 into CO and oxygen, an important step towards achieving the conversion of renewable energy into hydrocarbon fuels.
Self-healing catalyst films for hydrogen production
Chemists at the Centre for Electrochemical Sciences at Ruhr-Universität Bochum have developed a catalyst with self-healing properties.
Argonne scientists make vanadium into a useful catalyst for hydrogenation
In a new study, Argonne chemist Max Delferro boosted and analyzed the unprecedented catalytic activity of an element called vanadium for hydrogenation -- a reaction that is used for making everything from vegetable oils to petrochemical products to vitamins.
Researchers report new, more efficient catalyst for water splitting
University of Houston physicists have discovered a catalyst that can split water into hydrogen and oxygen, composed of easily available, low-cost materials and operating far more efficiently than previous catalysts.
Researchers develop eco-friendly, 4-in-1 catalyst
Performing multiple reactions in one shot reduces raw material needs and byproduct waste, a potential step toward a greener chemical industry.

Related Catalyst Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Changing The World
What does it take to change the world for the better? This hour, TED speakers explore ideas on activism—what motivates it, why it matters, and how each of us can make a difference. Guests include civil rights activist Ruby Sales, labor leader and civil rights activist Dolores Huerta, author Jeremy Heimans, "craftivist" Sarah Corbett, and designer and futurist Angela Oguntala.
Now Playing: Science for the People

#521 The Curious Life of Krill
Krill may be one of the most abundant forms of life on our planet... but it turns out we don't know that much about them. For a create that underpins a massive ocean ecosystem and lives in our oceans in massive numbers, they're surprisingly difficult to study. We sit down and shine some light on these underappreciated crustaceans with Stephen Nicol, Adjunct Professor at the University of Tasmania, Scientific Advisor to the Association of Responsible Krill Harvesting Companies, and author of the book "The Curious Life of Krill: A Conservation Story from the Bottom of the World".