Electron spin resonance studies of some bis(cyclopentadienyl) complexes of vanadium(IV) and niobium(IV)

Abstract

40 Complexes of the type [M(η⁵-C₅H₅)₂L₂]ⁿ⁺(M = V or Nb; L₂= one bidentate or two unidentate ligands; n= 1 or 0) have been studied by e.s.r, spectroscopy at room temperature and at 77 K. From the g and metal hyperfine tensors, the hyperfine parameter P, the spin-polarisation parameter, κ, and the orbital coefficients a and b were calculated. The unpaired electron is in an orbital of a₁ symmetry comprising ad_z²+bd_x²–y². Trends in these parameters are related to the interbond angle L–V–L and to the relative π-acceptor and π-donor character of L.