ELECTRON-PARAMAGNETIC RESONANCE STUDY OF DICHLOROBIS-(PI-CYCLOPENTADIENYL)TANTALUM(IV), (PI-C5H5)2TACL2

X-band EPR spectra of magnetically-dilute solutions of (π-C5H5)2 TaCl2 in chloroform have been recorded at 77 K and 298 K and are analysed in detail. The spin-Hamiltonian parameters have been extracted from the spectrum recorded at 298 K, and from spectra of magnetically-dilute glasses taken at 77 K. These parameters, and data obtained from visible-UV spectra, have been used to obtain quantitative descriptions of the bonding in this compound in terms of molecular orbital models. The unpaired electron lies essentially in the 5dx2 - y2 metal-ion orbital and is extensively delocalised onto the chlorine ligands. π-electrons of the cyclopentadienide rings and σ- and π-bonding electrons derived from chlorine ligands are almost completely delocalised. © 1979.