On the chemistry of sandwich complexes. XV. The ligand field theory, electronic spectrum and metal-ligand bonding in nickelocene

Absorption spectroscopy of (Ind)Ni(PPh3)X (Ind = indenyl, 1-Me-indenyl; X = Cl, Br, Me) and M(Ind)2 (M = Ni, Ru; Ind = indenyl)

“…In contrast, the first absorption band in Ni(Ind), is symmetric, indicating that one electronic state determines the band shape. These observations imply that the character of the lowest energy excited state of Ni(Ind), is not similar to that of nickelocene where all low-energy transitions are parity forbidden d-d bands (25). The large width for a single band is caused by large structural changes between the ground-and Can.…”

“…4 and their band energies and intensities are summarized in Table 1. The UV-visible spectrum of Ni(Ind), shows an intense, broad absorption band in the green spectral region with its maximum at 20 200 cm-' and a molar absorptivity of 3180 M-' cm-', very different from nickelocene whose lowest-energy absorption band is in the red spectral region with a first maximum at 14 500 cm-I and a much lower molar absorptivity of 60 M-' cm-I (23)(24)(25). The band maximum of Ni(Ind), is higher in energy by 5700 cm-' and more intense by almost two orders of magnitude than in nickelocene.…”

Electrophilic Double‐Sandwiches Formed by Interaction of [Cp2Fe] and [Cp2Ni] with the Tridentate Lewis Acid [(o‐C6F4Hg)3]

“…In an effort to provide a rationale for the dark red color of 3 which does not correspond to that of dark green nickelocene, we have recorded and analyzed the visible diffuse reflectance absorption spectra of 3 and nickelocene. The solution absorption spectrum of nickelocene has been reported19, 20 and is dominated by three intense spin‐allowed transitions at 426 ( 3 A 2g → 3 E 1g ), 589 ( 3 A 2g → 3 E 2g ), and 695 nm ( 3 A 2g → 3 E 1g ) as well as one weak spin‐forbidden transition at 526 nm ( 3 A 2g → 1 E 1g ). The diffuse reflectance spectrum of pristine nickelocene could be satisfactorily modeled on the basis of these four bands, with the spin‐forbidden 3 A 2g → 1 E 1g band being the weakest (Figure 3).…”

Crystal field approach to pentagonal-bipyramidal seven-coordinate complexes. Electronic structure of heptacyanovanadate(III)

“…This is the treatment of nickelocene (d8) in an axial (Dxh) ligand field by Pavlik, Cerny, and Maxova. 13 The same workers' treatment of d3,d7 sandwich complexes14 would be appropriate for the Mo(CN)74' complex if it is indeed of Dih symmetry.15 Ligand field calculations for ferrocene12 could be applied to d4,d6 pentagonalbipyramidal systems.…”

“…The results of the d2 D"h calculation13 for the strong-field case are presented in Table I, which may be derived from ref 13 by noting that the irreducible representations Alg, A2g, Elg, E2g, E3g, and E4g (notation of ref 13 forD"h) correlate with A/, A2) Ei", E2', E2", and E/, respectively, in DSh\ also, the sign of Ds must be changed and the parameters Ds and Dt converted to and 2 by use of eq 8. For the d8 electronic configuration, the signs of the crystal field parameters must be inverted.…”