The palladium (Pd) and ruthenium (Ru) species in several attractive catalysts have been probed using X-ray absorption spectroscopy (XAS). The study of catalyst evolution in suspension- and solution-based reactions was the primary aim. It was achieved by performing in situ XAS experiments on Pd and Ru over the course of the reactions. A custom-made reactor was employed which allowed the catalysts to be mixed with other reaction components under desired conditions.

The first system investigated was the Heck coupling reaction catalyzed by Pd(II) complexes embedded on metal-organic frameworks. It was realized that the as-synthesized catalysts go through an instant ligand substitution process when added to the reaction mixture. Mononuclear Pd complexes are the active species at the first stage of the measurement which then gradually transform into Pd nanoclusters. At a later stage of the measurement, chloride ligands start to bind to surface atoms of the Pd nanoclusters, leading to a deactivation of the catalyst. Following the first successful in situ XAS experiment, Pd(II) carbene complexes catalyzing undirected C–H acetoxylation of benzene in the presence of an oxidant were explored. A gradual ligand substitution occurs, and the mean oxidation state of Pd increases at the same time. At a later stage, Pd nanoclusters form, while the mean oxidation state of Pd returns to the start value. Deactivation of a heterogeneous Pd(II) catalyst during cycloisomerization of acetylenic acids was then investigated using in situ XAS. The choice of substrates showed to significantly influence the nature of Pd species, and the reduction of Pd(II) forming Pd(0) aggregates causes the deactivation. Moreover, strategies of reactivating the catalyst and prevention of the deactivation were developed and examined. In the end, the activation process of a Ru catalyst was studied and the structure of the intermediate was determined by in situ XAS. It was demonstrated that an electron-donating substituent on the cyclopentadiene ligand exhibits a promoting effect on the activation, while an electron-withdrawing substituent inhibits the activation.

The main focus of this thesis concerns the development of Pd(II)-catalysed synthetic methodologies for the preparation of biologically active compounds.

In the first part (paper I-III), unactivated C–H bonds of a cyclobutane derivative are selectively functionalised using a directing group starting from the feedstock compound verbenone (paper I). In the following part the development of an efficient transamidation protocol for the directing group removal is reported (paper II). Both procedures were then used in conjunction, for the synthesis of diverse C-3 arylated benzofuran-2-carboxylamides, in only 3 steps starting from benzofuran-2-carboxylic acid (paper III).

The second part (paper IV-V) aimed to evaluate the catalytic efficiency of the heterogeneous catalyst Pd(II)-AmP-MCF in the intramolecular hydroamination of propargylic carbamates. The catalyst was able to promote the formation of various 1,3-oxazolidin-2-ones in high yields, at room temperature with low palladium loadings (paper IV). This investigation is followed by a mechanistic study of the Pd(II)-AmP-MCF catalyst’s deactivation process during a lactone formation, using X-ray absorption spectroscopy (paper V).

The focus of this thesis is twofold: The first is on the application of iron catalysis for organic transformations. The second is on the use of in situ X-ray absorption spectroscopy (XAS) to investigate the mechanisms of a heterogeneous palladium-catalyzed reaction and a homogeneous ruthenium-catalyzed reaction.

In chapters two, three and four, the use of iron catalyst VI, or its analog X, is described for (I) the DKR of sec-alcohols to produce enantiomerically pure acetates; (II) the cycloisomerization of α-allenols and α-allenic sulfonamides, giving 2,3-dihydrofuran or 2,3-dihydropyrrole products, respectively, with excellent diastereoselectivity; and (III) the aerobic biomimetic oxidation of primary- and secondary alcohols to their respective aldehydes or ketones.

In the fifth chapter, XAS is used to elucidate the mechanisms of a Pd(II)-AmP-MCF-catalyzed lactonization reaction of acetylenic acids. The catalyst was known to deactivate during the reaction and the XAS studies identified the cause of this deactivation. A reactivation strategy was subsequently developed based on these findings.

In the sixth and final chapter, XAS is used to examine the activation mechanism of a ruthenium racemization catalyst and a ruthenium-acyl intermediate which had previously been speculated to be formed in the activation process was confirmed.