Our research is concerned with the design, assembly and understanding of molecular architectures that act as catalysts for sustainable chemical synthesis. The focus is placed on discovering and developing novel catalytic methodologies, aiming at:

We devise molecular metal catalysts and engineer the catalytic systems for target reactions, and we do this by an integrated approach, harnessing chemistry ranging from organometallics through synthetic organic chemistry to physical chemistry, and by close collaborations with leading pharmaceutical and chemical organisations. To have a taste of our research, you may wish to go on to the few selected examples below.

Hydrogenation and transfer hydrogenation are a most widely used technology for industrial chemical and pharmaceutical synthesis. We recently developed catalytic systems that allow these reactions to proceed in water in a fast, selective and productive fashion with no need for any organic solvents. Remarkably, some of these catalysts can be used for both hydrogenation and transfer hydrogenation. Commercial application of the aqueous-phase reduction is already underway.

Ever since its discovery, the Heck reaction has been mainly limited to electron-deficient olefins, leading to linear olefinic products. When electron-rich olefins are used, however, a mixture of regioisomers results, thus limiting its synthetic utility.

Realising the key to controlling the regioselectivity hinges on an ionic Pd(II) species, we discovered that the Heck coupling of aryl halides with electron-rich olefins can be accomplished in >99/1 regioselectivities in ionic liquids, which promotes the ionic mechanism and hence the regioselective formation of branched olefins. This chemistry has been extended to a wide range of electron-rich olefins, providing a novel avenue for many synthetically useful compounds. If ionic liquids are inaccessible to you, no worries! Further studies in our group have enabled common solvents to be used without the expensive ionic liquids. For instance, we reported that simple hydrogen-bond donors are highly effective in promoting the formation of the ionic Heck intermediate and hence the regioselective coupling reaction.

Mechanistic understanding of catalysis is key to the design of new enabling catalysts for green chemical and pharmaceutical manufacturing, and it satisfies our curiosity in nature and our desire in advancing chemistry. An example is seen in our work on the asymmetric transfer hydrogenation in water, where we showed a much faster reduction in water than in organic solvents. Mechanistic studies then revealed that water accelerates the hydrogenation by participating in the transition state via hydrogen bonding. However, the reaction is pH-dependent, with the active catalyst being protonated at low pH and forming hydroxyl species at high pH. So not only is water a green medium for the reaction, it is an active partner of the catalytic cycle as well.

Earlier, we showed that ionic liquids such as those based on imidazolium salts are not innocent spectators in catalysis. In particular, we demonstrated that hydrogen bonding in the ionic liquids can play a critical role in catalysis, and the imidazolium cations can in situ form catalytically active metal-carbene species.