We are interested in using a rational “bottom-up” approach for the design of new molecular systems with particular features or functionality. This may be with an application in mind e.g. as ionic liquids, catalysts, electrolytes in battery and fuel cells or in photovoltaic/electroluminescent devices. Alternatively, it may involve the synthesis and study of new species of fundamental interest. In addition to the study of new species, we are actively involved in mechanistic studies to understand the mode of action of currently available homogeneous catalysts with a view to improving their activity using combined experimental and computational methods.
This work involves many different aspects of chemistry including synthetic main-group chemistry, ionic liquids, organometallic chemistry, computational chemistry and catalysis.
We are always interested to hear from enthusiastic and tallented students and post-doctoral researchers looking to join the group (for PhD projects, post-doctoral positions, MChem research projects, Erasmus placements etc.). Please contact John Slattery (firstname.lastname@example.org) to discuss currently available projects.
Ionic liquids (ILs) are an interesting class of salts with surprisingly low melting points. They are often liquid at room temperature, which is remarkable considering the high melting points of classical inorganic salts such as NaCl (m.p. 800° C). ILs are usually composed of a relatively large organic cation in combination with a complex anion e.g. [EMIM]+[BF4]– (below).
The 1-ethyl-3-methylimidazolium cation (left) and tetrafluoroborate anion (right) form one of the more common room-temperature ionic liquids (often abbreviated [EMIM][BF4]).
ILs are currently attracting considerable attention, as their unique properties make them suitable for a wide range of applications. There is also considerable scope for modification of the cation and/or anion structure to tune the properties of an IL. We have recently developed some simple techniques to predict the physical properties of these materials. This promises to simplify the design of new ILs with particular properties tuned to specific applications. In recent collaborations with Prof. Ian Fairlamb (York), Prof. Ken McKendrick (Heriot-Watt) and Prof. Tim Minton (Montana State) we have designed "doped" ionic liquids with alkene functionality for Pd catalysis and probed the surface structure of ionic liquids using reactive oxygen atoms. We are also involved in an ongoing collaboration with Prof. Duncan Bruce (York) investigating the synthesis of new liquid-crystalline ionic liquids (LCILs) and their use as structured reaction media for pericyclic organic reactions.
Weakly coordinating ions such as those found in ILs also have applications in the stabilisation of reactive anions or cations of fundamental interest. One of our main goals is the synthesis of new and unusual main-group-element-containing ions. For example, we were able to investigate the coordination chemistry of low-valent gallium cations with very weak ligands by combining these cations with weakly coordinating anions (WCAs). These chemically robust, weakly basic anions do not compete with the ligands for metal coordination and also do not decompose in the presence of very electrophilic cations. Our WCA salts of Ga+ have allowed us to gain access to chemistry that was previously impossible using conventional sources of Ga(I) - for example the synthesis of the first example of a Ga(I)-phosphine complex [Ga(PPh3)3]+[WCA]-.
The crystal structure of an arene complex of Ga+ in combination with one of the best WCAs [Al(OC(CF3)3)4]–. Although the WCA is very weakly nucleophilic, some long range anion–cation interactions between Ga and F atoms are still present – there is no such thing as a non-coordinating anion!
Our work often involves the use of quantum chemical techniques alongside synthetic studies. Ab initio and density functional theory (DFT) methods can help in the interpretation of synthetic results e.g. by simulation of IR/Raman and NMR spectra, visualisation of molecular orbitals and investigation of reaction mechanisms. We have recently used DFT methods in combination with experimental studies to probe the mechanism of alkyne to vinylidene conversions at Ru and Rh centres. Theoretical studies were able to reproduce the experimental findings and give extra insight into the mechanism in the Rh system, including a survey of substituent effects that would have been very time consuming to perform experimentally. We were also able to identify a new mechanism in C-H activation chemistry, the ligand-assisted proton shuttle (LAPS) mechanism, where the ligand periphery around the metal centre is as important for the mechanism as the metal itself. This synergy between computational and experimental studies is key to a collaboration between our group and that of Jason Lynam, which aims to better understand and ultimately to design better homogeneous catalysts.
The potential energy surface for the alkyne to vinylidene transformation at Rh(PR3)2Cl. The simplest system studied is shown, but a variety of different substituents on the alkyne and phosphine ligands were investigated.
In collaboration with the group of Bernhard Breit in Freiburg, Germany we have also used DFT studies to examine the structural chemistry of supramolecular metallopeptide catalysts. These intriguing complexes incorporate phosphine ligands that mimic nature using various non-covalent interactions to self assemble chiral bidentate ligands with defined strutures.