Bonding and structure of Y3C2 and Y3C2+

摘要

Vibrational frequencies of yttrium normal modes of triyttrium dicarbide neutral and cation have been determined from pulsed field ionization-zero electron kinetic energy photoelectron spectra. The yttrium stretching mode has a frequency of 228 cm(-1) in the ion. The two deformation modes have frequencies of 82 and 24 cm(-1) in the neutral and a degenerate frequency of 85 cm(-1) in the ion. Geometries and ground electronic states have been determined by the comparison of the experiments and theoretical calculations. The cluster has a trigonal bipyramid structure with the ion symmetry of D-3h and the neutral C-2 nu. The ground state is identified as B-2(1) for the neutral and (1)A(1)' for the ion. While the Y-Y bonding has a covalent nature, the Y-C bonding has considerable ionic character. Both the Y-Y and Y-C bonds are stronger in the ion than in the neutral. The enhancement of the Y-Y bonding upon ionization is largely due to the removal of the antibonding 5s character from the yttrium atoms and the Y-C due to the increase of the electrostatic attractions between the yttrium and carbon atoms. (C) 1998 American Institute of Physics. [References: 30]