Gold Catalysis – the journey continues

Catalysis research represents one of the key technologies of the 21st century. As catalysis can lead to lower energy consumption, higher selectivity or even allows activation of dioxygen for oxidation reactions, it is an important facet of green chemistry. Catalysis is crucial to the well-being of society since over 80% of all manufactured materials at some point in their production require the use of a catalyst. Catalysts are therefore both useful and ubiquitous and there is always a need to find new improved catalysts.

Catalysis classically has been divided into two sectors, heterogeneous and homogeneous catalysis. Both sectors have their intrinsic advantages and drawbacks. The strength of heterogeneous catalysts is the separation of the catalyst and the stabilization of the catalyst by the support, which allows high turnover numbers. On the other hand, the complicated structure of the catalyst and the different species which simultaneously co-exist on the support create problems of the reproducibility of the catalyst preparation as well as analytical problems in trying to determine the nature of the active components. The detection of the different species and sites, the structural assignment and the correlation of specific species with the catalytic activity require a whole arsenal of – sometimes quite complex – analytical tools. Due to the diverse features which have to be studied, for example clusters of atoms and nanoparticles as well as sections of the support, these types of catalysts are highly challenging. In homogeneous catalysis the situation is almost inverted. The catalyst recycling is more complicated, in most cases the catalyst is destroyed at the end of the work up and has to be re-synthesized after separation. In many cases this only allows a batch-wise conversion. On the other hand, the catalyst structure is well defined and by normal tools of molecular chemistry can be assigned unambiguously. Computational chemistry allows a quite precise analysis of the electronic structure of the catalyst and of the intermediates of the reaction.

One of the newest arrivals in the field of catalysis is catalysis by gold which is the subject featured in this special issue. At present catalysis by gold is a burgeoning field with many hundreds of papers appearing annually for both homogeneous and heterogeneous catalyst reactions. Of course this has not always been the case and the perception of gold being the most noble of metals probably ensured that the real catalytic efficacy of this element was not uncovered until recently. In 2006 we published a review (A. S. K. Hashmi and G. J. Hutchings, Gold Catalysis, Angew. Chem., Int. Ed., 2006, 45, 7896–7936) that described how gold catalysis was showing great advances and we contrasted the approaches taken with homogeneous and heterogeneous gold catalysis. Since then there has been immense progress and in this special issue we collect a number of cutting edge papers on gold catalysis spanning a whole range of reactions and approaches. Gold catalysis still increases its potential for both the synthesis of bulk and fine chemicals in different sectors like platform chemicals, substrates with biological or medical activity or products for material science. And, in addition to the synthetic aspect, still new and fascinating mechanisms are discovered and new types of catalysts are developed. The papers in this special issue show how the field of gold catalysis still offers much scope for really innovative research and we expect this to continue in the future.

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