Cyclopentadienyl (Cp) cobalt(I) complexes rank among the "1st generation" catalysts for [2+2+2] cycloaddition reactions; however, only a small number of complexes are currently applied in practice and most of them require relatively high activation temperatures. We have synthesised an array of new cobalt(I)-olefin complexes and evaluated their high reactivity in cycloaddition reactions. The introduction of phosphites as ligands and the development of new synthetic methods led to a number of catalysts, which are active already at very mild temperatures and provide scope for systematic studies of the reactivity, depending on the ligand combination.
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Associated Group Prof. Marko Hapke (University Linz - Austria)
The liaison of unsaturated substrates containing C-C double or triple bonds and transition metal complexes provides the entry into a fascinating world of unusual reactions and the formation of a wide spectrum of different reaction products. The construction of molecules with high functionality and molecular complexity by transition metal-catalysed cycloaddition reactions, starting from alkynes and heteroatom-containing analogues, constitutes a very multi-faceted challenge. Therefore our particular attention is dedicated to the systematic praparation and characterisation of novel precatalysts based on group 9 metals and neighbouring metals like iron or nickel. Especially half-sandwich cobalt compounds and from them derived complexes can contribute significantly by studying their reactivity and underlying structural parameters. Insightful findings for the catalytic assembly of benzenes and heteroarenes by cyclotrimerization reactions were gained by comparison with the corresponding complexes of the heavier homologues rhodium and iridium as catalysts.
Additionally a major role is played by the task of investigatingCatalytic Cycloadditions the cobalt-catalysed asymmetric [2+2+2] cycloaddition for the enantioselective preparation of axially chiral biaryl derivatives. The photochemical conditions applied contrast the pure thermal reaction with exceptional results and observations. Due to the necessary preparation of the required substrates needed for the investigation of novel precatalysts, we have acquired extensive knowlege in the area of preparative alkyne and arene chemistry.