Fundamental Studies of Gold(III) Complexes With Hydrocarbon Ligands

This project has focused on the chemistry of organometallic complexes of gold. Gold is an element that receives considerable attention in contemporary chemistry research - in connection with catalysis, nanochemistry, electronics, and medicinal applications. It is of particular importance for this project that gold complexes are able to catalyze a wide range of new chemical transformations. In a longer time frame, these new catalysts may be of great practical and industrial value. For us, it has however been of more immediate importance that gold complexes are of great interest from a basic research perspective, as they offer new ways by which matter can be transformed. Hardly anybody would, a few years ago, have imagined that this usually so noble and apparently unreactive metal could find so many interesting applications! The chemistry of gold is truly a «hot» topic in international chemistry research, with many active research groups, fierce competition, and a steady flow of novel discoveries and innovations. In this research project, we have investigated fundamental properties of new gold complexes which may be of interest to catalysis. Whereas the grand majority of the gold complexes that are investigated and used for catalysis today comprise univalent gold, Au(+1), we have targeted the chemistry of trivalent gold, Au(+3). Complexes of Au(+3) have hitherto been much less available due to lack of efficient synthesis protocols. We have established in-house a series of robust methods for the preparation of the interesting molecular species that are the starting points for our investigations. The research has been developed with a highly desirable symbiotic relationship between experiment and theory: Experimental results are used as inspiration and input in theoretical studies which give us a much deeper understanding of the experimental results. Data from the theoretical studies then help us to arrive at a rational design of new and better compounds and experiments. The interplay between these two approaches now works magnificently. In fact, through this project we have raised this combined approach to a new level, such that theoretical and computational chemistry is now an integrated part of essentially all of our research activities. We have in particular been interested in developing and understanding reactions between gold complexes and small, organic molecules. Such small molecules serve as building blocks for the construction of more complicated structures and industrially interesting products. In 2013, we reported our successful preparation of the first and thus far only case of a fully characterized Au(+3) compound that is bonded to an alkene (alkenes are unsaturated compounds, meaning compounds that have carbon-carbon double bonds, and are of great industrial importance). In 2014, we published the discovery of a gold-assisted reaction in which the double bond was used as a building block in a larger molecule. This finding has been further developed, and we have demonstrated that a range of more complicated alkenes undergo similar transformations. In 2016, we demonstrated how several small molecules (ethylene, acetonitrile, water) may be activated and connected to a more complex structure in one step. The interplay between experiment and theory has provided us with a detailed insight into how these reactions occur. In 2017, we reported that this stoichiometric reaction with ethylene can be turned into a catalytic reaction if, instead of ethylene, acetylene is used as the feedstock. This all happens via a reaction mechanism which is unexpectedly complex and which could only be understood by means of the interplay between experiment and theory. We now have a level of mechanistic insight which gives us a good idea about what is needed to turn the reactions of alkenes into catalytic processes, too. This must however be delegated to future research projects. The gold complexes that are synthesized, are studied by others via European networks and student exchange. Some of the complexes are of interest with respect to medicinal applications, and collaboration efforts are in the early startup phase. The project has strongly contributed to our active participation in 3 EU COST-actions and in a recently started EU Marie-Curie-Sklodowska ITN network in nanotechnology.

This project will focus on fundamental gold chemistry with a focus on gold(III). Gold chemistry is a very 'hot' research area, particularly within solution chemistry and homogeneous catalysis. The focus internationally has been mostly on gold(I) compounds , which have been found to catalyze a diverse range of organic transformations. Gold(III) has received much less attention and we seek to rectify this situation. The project will ensure a continuation of cutting-edge research in the Oslo cluster of organo metallic researchers. This project is built upon recent results obtained in the nearly completed GULLMAKS project (financed by the GASSMAKS program of the Research Council of Norway), which aimed to develop Au complexes capable of activating C-H bonds in light alkanes, and associatied activities. The new proposed project, like the GULLMAKS project, will productively integrate experimental and theoretical approaches. The project will have the following main foci: - Experimental and theoretical studies of the synthesis and reactivity of neutral and cationic gold(III) complexes that bear cyclometallated heteroaromatic ligands and hydrocarbon-derived ligands (alkyls, aryls, alkynes, alkenes, arenes, and alkanes); - Exploitation of these compounds in Au(III) -catalyzed organic transformations.