Parametric Analysis of the Crystal Field Splitting Pattern of Pr(η5-C5Me5)3

Electronic structures of organometallic complexes of f elements LXXXIII: First comparison of experimental and calculated (on the basis of density functional theory) polarized Raman spectra of an oriented organometallic single crystal: Tris(pentamethylcyclopentadienyl)lanthanum

The polarized Raman spectra of an oriented La(η(5)-C5Me5)3 (1) single crystal (where the principal axes of the two molecules per unit cell are uniformly oriented) as well as the mid (ca. 90K) and far infrared spectra of pellets have been recorded. Applying the selection rules of C3h symmetry to the spectra obtained, the irreducible representations (irreps) of numerous lines/bands of intra-ligand character were derived. In the range <400cm(-1), where 28 Raman-allowed lines and 20 FIR-allowed bands of both skeletal and intra-ligand character are expected, only few assignments based on symmetry considerations were possible. In order to increase the number of identifications, model calculations on the basis of density functional theory (DFT) were performed. In the intra-ligand range >400cm(-1), the obtained results agree well with the experimental findings. Because of the strong mixing at lower wavenumbers, even the separation of calculated skeletal and intra-ligand modes and the identification of the former was only successful by comparing the calculated FIR and averaged Raman spectra of compound 1 with those of La(η(5)-C5Me4H)3 (2). Making use of both the calculated frequencies of normal modes and their polarizability tensors, the polarized Raman spectra of an oriented single crystal of 1 in the range <400cm(-1) were calculated and compared to the experimental ones. Because of an overestimation of the mixing of normal vibrations of A' symmetry, the experimental intensities of the lines of the symmetric stretch ν1(A') were not reproduced by the calculation for compound 1 but by that for Sm(η(5)-C5Me5)3 (3). Skeletal and intra-ligand modes were separated and designated. Neglecting νC-H modes, the DFT calculation for 1 achieved an r.m.s. deviation of 17.9cm(-1) for 72 assignments.

Variable photon energy photoelectron spectroscopy of tris-cyclopentadienyl lanthanides

Gas-phase photoelectron spectra are presented for LnCp₃ (Cp = η-C₅H₅; Ln = Pr, Nd, Sm) in which f ionization gives rise to bands associated with 4fⁿ configurations in addition to the expected 4fⁿ⁻¹ bands.

Electronic structures of organometallic complexes of f elements LXXVI: Correlation of experimental and calculated (on the basis of density functional theory) vibrational spectra of bis(η5-cyclopentadienyl)ruthenium and bis(η5-pentamethylcyclopentadienyl)ruthenium

Previous empirical assignments of the normal modes of Ru(η(5)-C(5)H(5))(2) were checked against the results of a calculation applying density functional theory (DFT). After some reassignments, following those recently suggested for Fe(η(5)-C(5)H(5))(2) (after theoretical model calculations), a satisfactory agreement was observed. Recently communicated polarized Raman spectra of an oriented Ru(η(5)-C(5)Me(5))(2) single crystal were used here for the identification of the irreducible representations of a number of Raman active normal modes (assuming molecular D(5h) symmetry) which agree well with the results of the DFT calculation. The energies of IR active fundamental vibrations, extracted from recently communicated FIR/MIR spectra (pellets), were correlated with comparable energies of IR allowed irreducible representations of the DFT calculation and assigned. Both the skeletal and the intra-ligand normal modes could be correlated with the idealized standard motions (ν(i)s) of the model sandwich complex Ru(C(5)C(5))(2), and previous assignments had to be revised. Neglecting the νCH vibrations (which are off by ca. 50cm(-1)) an r.m.s. deviation of 9.8cm(-1) (for 47 assignments) of the remaining normal modes could be achieved.