A multi-diverse approach to catalysis : ruthenium, gold and FLP catalysis

Abstract

Ruthenium-based homogenous catalysis is a broad and extremely useful branch of transition metal catalysis. Surely, the most famous example is olefin metathesis, for which Yves Chauvin, Robert Grubbs and Richard Schrock were awarded the 2005 Chemistry Nobel Prize. Although some of the most well-known catalysts are widely used and considered benchmark catalysts, the research around this topic has not stopped. The modification of known systems to achieve better performance and better understanding of the catalytic mechanism is very important and an example of such modification is reported in this thesis. The newly synthesised catalysts were compared to the parent commercially available catalyst showing better reactivity. Ruthenium catalysis, though, is not limited to olefin metathesis and C-H activation, for example, it has become a useful approach to the functionalisation of organic molecules. In this field, the deuteration of C-H bonds is an interesting transformation, which has many applications. The synthesis of new hydridosilylruthenium complexes and their application in the deuteration of a variety of substrates is reported in this manuscript. The unprecedented synthesis of tetradeuterated Ketoprofene is also reported. Recently, ruthenium-based catalysts have found application in the dehydrogenation of suitable compounds, such as formic acid, ammonia-borane and other hydrogen-rich substances. The driving force behind these discoveries is the use of H₂ as an energy vector in place of fossil fuels. A hydrido-ruthenium catalyst was shown to catalyse the decomposition of formic acid in CO₂ and H₂ and to catalyse the reduction of olefinic substrates. The released CO₂ from the reaction did not interfere with the fuel cell due to its inertness. This property makes its employment as C1 source very challenging, although its use would also be extremely attractive because of the abundance of this gas. In these regards, both frustrated Lewis pairs (FLPs) and gold catalysts have shown interesting reactivity in the activation of CO₂. A new FLP and a silica supported gold catalyst were synthesised to test them in CO₂ activation and the results are reported in this manuscript.