Gold is a metal that most people can relate to in some way. When we were young, we met gold in fairytales and comic books. Many of us may remember Scrooge McDuck diving in his gold coins, or what about the chase for gold at the end of the rainbow? But what many people don't know is that gold is so much more than just a metal used for decoration and for showing wealth. For a long time, it was believed that gold was just a boring metal of no particular use, but during the last decades the interest in gold has increased rapidly, and there are now research groups across the world working with gold and its rich chemistry. So far, applications of gold have been found within medicinal chemistry, electronics and catalysis to mention some. In this project, we have studied a completely new class of organogold complexes which was recently discovered by us, namely gold(III) pi-allyl complexes. pi-Allyl complexes of other transition metals such as palladium and platinum has already been studied thoroughly, one well-known example being the palladium catalyzed "Tsuji-Trost reaction". In this project, we have developed a new method for synthesizing gold(III) pi-allyl complexes via sigma-cyclopropyl to pi-allyl rearrangement upon liberating a coordination site at gold. Mechanistic studies have shown that the rearrangement occurs via a disrotatory electrocyclic ring opening of the distal C-C bond in the sigma-cyclopropyl complex. The results from this project together with results obtained prior to the project has given us a broad insight into gold(III) pi-allyl complexes which we have summarized in a review discussing everything from synthesis and structure to reactivity and applications of these complexes. In addition to the studies on gold(III) pi-allyl complexes, we have also studied the mechanism and applications of gold(III) catalyzed hydroarylation of alkynes. The results achieved during this project gives important insight opening up new avenues within gold catalysis and organometallic chemistry, which is important for the development of new sustainable industrial processes.
During this project we have gained a significant increase in the knowledge of organogold chemistry, which has a direct impact on the rapidly growing community of gold chemistry and catalysis. With the newly discovered class of gold complexes with a n3 allyl ligand, Au(III) pi-allyl complexes, we have opened up a whole new branch in organogold chemistry and we now understand much more about their synthesis, properties and reactivity as well as their differences and similarities comparing them to other metal pi-allyl complexes. Onwards, the mechanistic studies of the gold(III) catalyzed alkyne hydroarylation has given us important insight into this reaction and stands out as one of the few examples of thorough in-dept studies of Au(III) catalyzed processes providing important knowledge essential for the further development of gold catalysis. As gold complexes are quite tolerant towards air and moisture, and the fact that mild conditions often can be used, makes the development of catalytic processes using gold very attractive and of high importance for the development of new sustainable industrial processes which is of significant importance for the society in general.
To achieve sustainability in the chemical industry catalysis is of utmost importance. The development of efficient industrial processes relies on the understanding of the fundamental chemistry of the catalysts used for these processes. Transition metal n3 allyl complexes are key intermediates in a variety of catalytic organic transformations, such as the very powerful and widely used Pd-catalyzed Tsuji-Trost reaction. The understanding of such complexes in terms of structure, dynamics and reactivity is crucial for the synthesis of advanced organic molecules. Gold was for a long time considered useless in catalysis, but has in fact turned out to be a very useful and unique transition metal, and gold catalysis has spectacularly developed over the last 2-3 decades. The involved organogold complexes are of particular interest due to their moderate to low sensitivity towards air and moisture, to their great functional group tolerance combined with the mild reaction conditions in which they operate.
In this project, the access to and fundamental chemistry of Au(III) n3 allyl complexes will be adressed. Au(III) n3 allyl complexes have been very scarcely described in the literature and during a recent project funded by the Research Council of Norway, we reported one of the first examples of Au(III) n3 allyl complexes characterized by NMR spectroscopy and X-ray crystallography. During this project several important and complementary aspects will be addressed. First, it is desired to learn more about the fundamental chemistry of the Au(III) n3 allyl complexes; how does the allyl ligand bind to the Au(III) complex, and how does these complexes behave compared to other related transition metal complexes? The synthetic scope and limitations will be investigated together with the reactivity of the complexes. Following this, work towards acheiving catalysis involving these complexes will be performed.
