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Polynuclear Gold Catalysis

Periodic Reporting for period 1 - GOLDCLUSTER (Polynuclear Gold Catalysis)

Reporting period: 2016-06-27 to 2018-06-26

•What is the problem/issue being addressed?

During the last decade, homogeneous gold catalysis has witnessed rapid growth for C–C bond forming reactions. Most of the gold catalysts used in these reactions were mononuclear complexes. Despite some pioneer work, the study of well-defined small gold clusters remains largely unexplored. In this project, we planned to prepare new types of highly electrophilic small gold clusters (3-8 Au atoms) with potentially enhanced catalytic properties that could have a significant impact in the advancement of the gold catalysis field and the development of more efficient and environmentally friendly synthetic methods.

•Why is it important for society?

One of the main challenges that the European chemical industry (one of the biggest in Europe) is facing nowadays is the reduction of the energy consumption of the chemical processes. Although the amount of energy consumed in 2012 was 16% less than in 1990, the fuel and power consumption of the EU chemical industry, including pharmaceuticals, amounted to 56.6 million tonnes of oil equivalent (TOE). The long-term objective of this project is to contribute to the development of low energy efficient procedures (lower reaction temperature, more efficient catalysts, and better yields), which could be adapted by the Chemical Industry, making the European economy more competitive and better aligned with the Horizon2020 growth strategy. Working in a new area of development could lead to discover breaking advances in catalysis, adding to excellence in the research European area and opening new opportunities for me and the future steps in my career.

•What are the overall objectives?

GOLDCLUSTER aims at advancing the field of gold chemistry. The major goal is to develop small polynuclear gold clusters as new superelectrophilic gold(I) catalysts and then explore their catalytic reactivity in organic transformations for the construction of molecular complexity using relatively simple starting materials.
In the two years’ project, we have already developed a simple method to synthesize a series of new tetranuclear [AuI]4 complexes in one step from simple starting material dppnAu2Cl2 (dppn = 2,9-bis(diphenylphosphino)-1,8-naphthyridine). Exploration of the catalytic activity of these new gold complexes showed that dppn2Au4R2(BArF4)2 (R = 3,5-(CF3)2C6H3) was highly selectively active in the cycloisomerization reaction of 1,6-enynes, while dppn2Au4Cl2(PF6)2 was found to be a highly efficient catalyst in formal [4+2] cycloadditions, obtaining the two desired products in 83% and 77% yields, respectively. For the cycloisomerization of 1,6-enynes, we have improved the products selectivity from 1:1.6 to 1:0 compared to our previous report. Besides, we have discovered an unprecedented intermolecular Au(I)/Au(I) transmetalation-type reaction. Preliminary studies on the mechanism of this reaction have been carried out. This work is not being completed and will be continued by another member of the research group. The results will be submitted for publication soon. These new gold clusters could also be applied to other useful organic transformations to construct complex molecules in the future, which will be used for the synthesis of numerous biologically active targets. We also expect that these new polynuclear gold clusters could have a significant impact in the advancement of the gold catalysis field and they can further contribute the development of more efficient and environmentally friendly synthetic methods for industrial applications.
On the scientific side, I have developed a simple method to synthesize a series of new gold(I) clusters that could be used in the cycloisomerization and formal [4+2] cycloaddition reactions of 1,6-enynes, leading to the formation of complex molecules. This project has contributed greatly to the advancement of gold chemistry by exploring new directions in the area and providing new tools to further enhance the development of efficient synthetic methods that could be later applied in industrial processes.

On the personal side, I have increased my capacities as a researcher while executing this project with the acquisition of complementary scientific skills (synthesis of Au complexes, increasing organometallic knowledge and skills, X-ray analysis, etc.) and non-scientific skills (research project management and scientific writing/presentation skills, industrial environment awareness, IPR management and science outreach). I presented my research results as posters (with the acknowledgements to the Marie Curie Grant) on 4 International conferences: XXXVI Biennial Meeting - Spanish Royal Society of Chemistry; 254th American Chemical Society National Meeting & Exposition; German-Spanish Symposium on Frontiers in Chemistry and Institute of Chemical Research of Catalonia (ICIQ) School. On the one hand, I improved my communication skills and had the chance to exchange ideas with people who work on different research field; on the other hand, I took the responsibility for the dissemination of MARIE SKŁODOWSKA-CURIE ACTIONS. Altogether, after the realization of GOLDCLUSTER, I have obtained essential skills to undertake the next step in my research career: leading my own research projects. All in all, GOLDCLUSTER has advanced the field of gold chemistry, meanwhile, the researcher has obtained essential skills for his independent research career.