Ruthenium complexes of chiral tridentate ligands: a new class of catalyst for asymmetric ketone and imine hydrogenation.
Lead Research Organisation:
University of St Andrews
Department Name: Chemistry
Abstract
A catalyst allows the rate of a chemical reaction to be accelerated enormously, without the catalyst itself being used up in the reaction. Homogeneous catalysts play an ever-increasing role in industrial chemical synthesis. The demand for chemical processes to be less harmful to the environment has increased the importance of reactions that utilise tiny amounts of catalyst to promote clean, efficient reactions between two chemicals that do not normally react with each other at a measurable rate. One of the most important examples is catalytic reduction of a class of chemicals called carbonyl compounds to alcohols. Alcohols are one of the most important ingredients for drugs, flavours, fragrances and plastics. There are a number of methods to do this transformation, but most generate waste. More desirable from an economic and ecological point of view is to use a catalyst and molecular hydrogen to accomplish this task, since no waste would be formed. This has been achieved for certain classes of carbonyl compound. However, there are many classes that are not efficiently 'hydrogenated' using the current state of the art catalysts. This research project aims to develop a new type of hydrogenation catalyst that is based on ruthenium metal compounds modified with an (optically pure) ligand containing phosphorus and nitrogen atoms. The new catalysts will efficiently hydrogenate ketones to alcohols. Some alcohols exist as two mirror image structures (optical isomers),related like your left and right hands, and despite sharing the same chemical composition, each mirror image has very different biological properties. There is therefore a massive research effort aimed at producing optically active alcohols as single optical isomers for the pharmaceutical industry. It is desirable that the methods used to prepare the single optical isomer alcohols use clean catalytic chemistry due to the environmental issues raised above. This project aims to develop catalysts that can cleanly hydrogenate carbonyl compounds that are currently difficult to reduce, and to do so in a way that makes a single optical isomer. The research could lead to new alcohols products being efficiently prepared for the first time, and could lead onto commercial applications in the future.
Organisations
People |
ORCID iD |
Matthew Clarke (Principal Investigator) |
Publications
Carpenter I
(2012)
Convenient and improved protocols for the hydrogenation of esters using Ru catalysts derived from (P,P), (P,N,N) and (P,N,O) ligands.
in Dalton transactions (Cambridge, England : 2003)
Clarke M
(2010)
Enantioselective Reduction of Benzofuranyl Aryl Ketones
in Synlett
Díaz-Valenzuela MB
(2009)
Enantioselective hydrogenation and transfer hydrogenation of bulky ketones catalysed by a ruthenium complex of a chiral tridentate ligand.
in Chemistry (Weinheim an der Bergstrasse, Germany)
Fuentes J
(2011)
On the rate-determining step and the ligand electronic effects in rhodium catalysed hydrogenation of enamines and the hydroaminomethylation of alkenes
in Catalysis Science & Technology
Phillips S
(2011)
Exploring the role of phosphorus substituents on the enantioselectivity of Ru-catalysed ketone hydrogenation using tridentate phosphine-diamine ligands
in Catalysis Science & Technology
Phillips SD
(2010)
On the NH effect in ruthenium-catalysed hydrogenation of ketones: rational design of phosphine-amino-alcohol ligands for asymmetric hydrogenation of ketones.
in Chemistry (Weinheim an der Bergstrasse, Germany)
Description | This project enabled us to develop new second generation catalysts for the hydrogenation of carbonyl groups. A mechanism-led approach was used, and kinetic data was obtained that led us to propose a mechanism for the reaction that actually enabled us to consider a broader range of catalyst structures. Studies were carried out that were designed to confirm or overturn this mechanism and in addition to confirming our proposal, developed yet further catalysts. While we chose to continue adding data after the project finished in some cases, there are now 7 publications in respected international journals resulting from the project directly, and a recent further publication (not linked here) that was directly built on these results. The programme is still active, and has moved into some other adjacent areas. The most noteworthy new development is that some of the compounds used as ligands during this initial phase were investigated using earth abundant, indefinitely sustainable manganese as the metal in place of ruthenium or iridium. This produced what may well be the most effective hydrogenation catalysts made using an earth abundant metal. It is quite possible that this un-anticipated application of the science developed in this programme will be the most important. This is being developed with a view to commercial application in the medium term. |
Exploitation Route | The findings were taken forward by others. When we started the broader class of catalyst design (tridentate ligand metal catalyst) was extremely rare, but now appears in hundreds of papers (possibly thousands). The more specific catalyst design, metal catalysts for hydrogenation derived from P,N,N ligand has appeared quite often in significant papers in the literature. More indirectly, we were one of the first groups to help popularise an important type of hydrogenation reaction as being a solvable challenge, which is now considered a hot area for catalysis research. The catalysts we made have been sold/provided to several industrial companies and hence used in their portfolio of solutions. The more recent discover taking the same compounds but combining them with Manganese instead of Ru is likely to have a significant impact. |
Sectors | Chemicals,Environment,Manufacturing, including Industrial Biotechology |
Description | Small samples of the catalysts were provided (sold or bartered) to three industrial companies, and hence are available for use in their catalyst testing programmes. Very recently, we have made use of the ligands produced in this work with a more sustainable earth abundant metal, and a collaboration aiming towards commercialisation has been established with a different technology provider. They are making a contribution in kind, valued at £70k, to our research in this area. |
First Year Of Impact | 2014 |
Sector | Chemicals,Manufacturing, including Industrial Biotechology |
Impact Types | Economic |