An Ylidic Cp and its Scandium Complexes in Equilibrium

Scandium complexes bearing a C-ylidic, electron-deficient Cp ligand are presented by starting from [ScCl3(thf)3]. As ylidic ligands do not require salt metathesis, the coordination of the Cp ligand is realized by mere substitution of the tetrahydrofuran ligands. In acetonitrile an equilibrium among the free ligand, the half-sandwich complex, and the cationic metallocene with its tetrachloridoscandate counterion is observed via NMR spectroscopy. This equilibrium is fully confirmed by 1H and 45Sc NMR EXSY experiments. In the absence of coordinating solvents, the selective formation of all compounds of the equilibrium has been achieved, and the structures have been confirmed by NMR spectroscopy and X-ray structure analysis. Especially 45Sc NMR spectroscopy reveals signals with characteristic chemical shifts for the half-sandwich complex and the metallocene. With scandium triflate the corresponding scandocene is also accessible.