NIOBOCENE DICHLORIDE AND NIOBOCENE DIIODIDE - ELECTRONIC ABSORPTION-SPECTRA AND ELECTRON-SPIN-RESONANCE

The effect of the halide ligand on the bonding of niobium in niobocene dichloride and niobocene diiodide was investigated. The electronic ab sorption spectra of the two compounds in the range of d-d transitions were resolved into four bands corresponding to transitions of the d(1) electron between five frontier orbitals in a molecule of symmetry poi nt group C-2v. The energies of the frontier molecular orbitals were de termined relatively to the energy of the orbitals in the spherically s ymmetric ligand field formed by the appropriate halide ligands. The ef fect of the halide ligands on the spin-orbital interaction of the HOMO orbital is discussed qualitatively on the basis the ESR spectra.