General valence force fields of the free and the coordinated cyclopentadienyl anion

Abstract The modified general valence force field (GVFF) of the free cyclopentadienyl (Cp) anion was developed with internal coordinates to perform the normal coordinate analysis (NCA). Further it is shown that it is possible to transfer the GVFF of the free ring to the coordinated form. The NCA and the GVFF of (Cp)Tl with inclusion of the ring ligand is presented for the first time. Good agreement between observed and calculated wavenumbers has been achieved for both model calculations, the (Cp)K and the (Cp)Tl. The force fields together with force constants and potential energy distribution are given.