Organotransition metal chemistry and homogeneous catalysis
Ola Wendt, Inorganic Chemistry

Our work falls in the field of organotransition metal chemistry and the goal is to find and develop organometallic reactions with a possible application in homogeneous catalysis and to define their reaction mechanisms in as much detail as possible. Thus we hope to be to able understand the factors which govern the choice of pathway and reactivity with the aim of developing reactions and catalysts in a rational manner. We also want to increase our understanding of the relation between structure and reactivity in organometallic systems. Synthesis and structural characterisation are of course important parts of any organometallic project. The mechanistic investigations will be accomplished by means of, inter alia, kinetics measurements and spectroscopic identification of intermediates. The experimental work includes techniques such as dynamic NMR and time-resolved rapid UV/Vis and IR spectroscopies. We are studying a number of reactions, which mainly fall into two categories: activation of small molecules and cross-coupling reactions. We are trying to find transition metal complexes for the activation of carbon dioxide to make new C-O and C-C bonds. Thus, we are assessing the reactivity of M-C and M-O bonds of various group 4 and 10 complexes towards CO2. Especially cyclometallated palladium complexes have shown a large potential in these reactions. Eventually the goal is to incorporate these reactions into catalysis making carboxylic acids and organic carbonates. These reactions are interesting from a feedstock point of view; their realisation would mean one step towards the use of renewable carbon sources for the chemical industry. From a "green chemistry" point-of-view these reactions are further interesting, since the making of carboxylic acids from hydrocarbons and CO2 is a no-waste, 100% "atom-economy" reaction and organic carbonates can function as replacements for highly toxic phosgene.. Cross-coupling reactions are versatile for making e.g. new C-C bonds and our work in this area has so far focused on the Stille reaction, especially the transmetallation step. However, our work on cyclometallated complexes in CO2 activation has cross-bred to this sub-project; these compounds were recently shown to be very active cross-coupling catalysts. It has been suggested that they operate by a different mechanism than classical Pd(0)-Pd(II) catalysts and this has been the topic of some debate. Our results so far point to a classical mechanism but we still don't know the generality of this conclusion.