Collect. Czech. Chem. Commun. 1998, 63, 628-635

Niobocene Dichloride and Niobocene Diiodide: Electronic Absorption Spectra and Electron Spin Resonance

Jana Holubová, Zdeněk Černošek and Ivan Pavlík

Department of General and Inorganic Chemistry, Faculty of Chemical Technology, University of Pardubice, 532 10 Pardubice, Czech Republic


The effect of the halide ligand on the bonding of niobium in niobocene dichloride and niobocene diiodide was investigated. The electronic absorption spectra of the two compounds in the range of d-d transitions were resolved into four bands corresponding to transitions of the d1 electron between five frontier orbitals in a molecule of symmetry point group C2v. The energies of the frontier molecular orbitals were determined relatively to the energy of the orbitals in the spherically symmetric ligand field formed by the appropriate halide ligands. The effect of the halide ligands on the spin-orbital interaction of the HOMO orbital is discussed qualitatively on the basis the ESR spectra.

Keywords: Sandwich complexes; Metallocenes; Niobocene dihalides; Electronic structure; d-d Spectra; ESR; EPR spectroscopy.