Synthesis of non-racemising twofold benzanullated fluorenide complexes and their application in stereoselective catalysis

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The synthesis of intrinsically chiral cyclopentadiende ligands is in the focus of this project. In this context, the meaning of intrinsically chiral is that the element of chirality is part of the cyclopentadienide ring. Transition metal compounds derived from these ligands will be investigated in stereoselective catalysis.Anullation of e.g. fluorenide with further ring structures in the right position leads to extended pi-systems, which contain both, a cyclopentadienide unit and a helicene type structure. Such ligands are of axial chirality, the axis is on one of the C-C bonds of the cyclopentadienide. From preliminary investigations we know, that the basic structure of this type of ligands, the 7H-dibenzo[c,g]fluorene, will equilibrate rapidly at room temperature. Analogue ligands with an increased barrier of racemisation will be interesting for stereoselective catalysis. They will be accessible by increasing the steric hindrance in the ligand backbone. By screening the literature we have identified three different possible routes leading to such ligands. Furthermore there are precursors or analogue systems in the literature for which the resolution of the racemates have been described. Catalytic activity of cyclopentadienide complexes is well-known for many transition metals. As far vas we know, there is no example for an intrinsically chiral cyclopentadienide that was applied in stereoselectiv catalysis. With this project we will be able to elucidate for the first time, whether this strategy will lead to success.