An electron paramagnetic resonance study of tetracyclopentadienyltantalum(IV), [Ta(σ-C5H5)2(η-C5H5)2]

Abstract

X-Band e.s.r. spectra of magnetically dilute solutions of [Ta(σ-C₅H₅)₂(η-C₅H₅)₂] in CHCl₃ have been recorded at 77 and at 298 K and are analysed in detail. The spin-Hamiltonian parameters are listed, and are equated to the atomic orbital coefficients in the molecular orbitals involved in bonding. The unpaired electron lies essentially in the 5d_x²-y² metal-ion orbital and it is extensively delocalised on to the cyclopentadienide rings. The σ and π electrons of the cyclopentadienide rings are almost completely delocalised.