On the chemistry of sandwich complexes. XVI. The ligand field theory for dicyclopentadienyl d3 and d7 complexes. The d-d transitions and ligand field parameters of vanadocene and some complexes of Cr(III)

Vanadocene de Novo: Spectroscopic and Computational Analysis of Bis(η5-cyclopentadienyl)vanadium(II)

“…The onset of more intense features in the near-UV region is marked by the steep rise in absorption at ∼29 000 cm −1 . This spectrum is qualitatively similar to those previously reported, 3,52,53 although the absorption spectrum collected here shows greater resolution for the lowest energy feature than for those previously reported. It is possible that in earlier studies there was light scattering from the frozen solution.…”

“…In our absorption spectrum, there are three bands of comparable intensity (ε ≈ 35–40 M –1 cm –1 ) in the visible region that are well modeled with three Gaussian bands centered at 17 000, 19 860, and 24 580 cm –1 (Supporting Information, Figure S4 and Table S1) . These three bands were previously assigned as spin-allowed 4 A 2g → 4 E 1g (I), 4 A 2g → 4 E 2g , and 4 A 2g → 4 E 1g (II) transitions, respectively, using symmetry labels from the D 5 d point group. , The 4 E 1g (I) and 4 E 1g (II) excited states are from the 4 F and 4 P d 3 free-ion terms, respectively. The 4 A 2g ground state of VCp 2 arises from the (a 1g ) 1 (e 2g ) 2 (e 1g ) 0 configuration, and the 4 E excited states arise from one-electron excitations.…”

“…Another LFT model was used by Pavlı́k et al, which is based on treating the D 5d symmetry metallocene (and analogous D 6 d bisarenes) effectively as a C ∞ v system. This approach has been thoroughly discussed in a number of papers by Warren ,− and will not be expounded on here.…”

“…This approach has been thoroughly discussed in a number of papers by Warren ,− and will not be expounded on here. We have, however, used the LF parameters derived by Pavlı́k et al, also to model successfully the electronic transitions and added SOC. This process is described in detail in the Supporting Information (see Tables S11 and S12).…”

Spectroscopy in the Ultraviolet and Visible Regions As Studied by Solution-Phase and Vapor-Phase Photoabsorption in the Ultraviolet and Visible Regions

“…The values of Δ 1 for the compounds considered are unknown. However, for (Ch)(Cp)V, the Δ 1 magnitude derived from the electronic absorption spectrum of vanadocene , (∼17 000 cm -1 ) can be used since this parameter depends mainly on the interaction between the metal d orbitals and MOs of the Cp ligand. − Taking the ratio C / B ∼ 4, which is usually accepted for transition-metal complexes, we can predict energies for all d−d transitions in (Ch)(Cp)V. Assuming Δ 1 /Δ 2 ratios in (Ch)(Cp)V and (Ch)(Cp‘)Ta to be similar, we find Δ 1 for the tantalum compound to be 24 400 cm -1 . Then it becomes possible to estimate the energies of the d−d transitions terminating at the MO d(π) of (Ch)(Cp‘)Ta.…”