The electron spin g-and hyperfine tensors of the endohedral metallofullerene Sc@C 82 are anisotropic. Using electron spin resonance (ESR) and density functional theory (DFT), we can relate their principal axes to the coordinate frame of the molecule, finding that the gtensor is not axially symmetric. The Sc bond with the cage is partly covalent and partly ionic.Most of the electron spin density is distributed around the carbon cage, but 5% is associated with the scandium d yz orbital, and this drives the observed anisotropy. PACS: 61.48.+c, 71.20.Tx, 33.35.+r, 31.15.Ew

The effect of methylation of ligands in bis(q6-benzene)chromium (1) on the strtlcture of Rydberg transitions in absorption spectra has been studied. A detailed analysis and interpretation of all Rydberg elements of the vapor-phase spectra of bis(-q6-toluene)chromium (2), bis(q6-0-xylene)chromium (3), bis(q6-m-xylene)chromium (4), and bis(q6-mesitylehe)chromium (5) was carried out. The vapor-phase electronic absorption spectrum of bis(rl6-p-xylene)chromium (6) was measured, and the assignment of the Rydberg bands was made for the first time_ The first ionization potentials of complexes 2--5 were refined. The energy of detachment of the 3dz~ electron and the parameters of the Rydberg excitations for molecule 6 were determined. The vibronic components of the 3dz2~R4px,y transition in the spectra of complexes 2. and 6 were assigned. The differences in the Rydberg structure of the spectra of compounds 2--6 were analyzed in terms of the selection rules for optical transitions in the corresponding symmetry groups. The vapor-phase spectra correspond to conformers with the symmetry groups C2~ and C~ for complexes 2--4, with the symmetry groups D31 , and D 3 for compound 5, and with the symmetry group D2d for complex 6.Sandwich complexes of transition metals are of interest as objects for studying by electronic absorption spectroscopy because they represent the only class of organometallic compounds whose vapor-phase absorption spectra have clearly defined Rydberg bands. Rydberg transitions can form series that converge to the ionization limit. The frequencies of the members of the series are described by the well-known Rydberg formula: t v n = I-R/(n-,5) 2 = I-R/(n*) 2 = I-T, where / is the energy of detachment of an electron from the orbital involved in the Rydberg transition (ionization limit); R is the Rydberg constant (109737 cm-t); n is the principal quantum number; 8 is the quantum defect; n* is the effective principal quantum number; and T is the term value (the energy of binding of the Rydberg electron with the cationic core).The Rydberg series can be assigned to particular transitions based on the quantum defects. The assignmeat of low-lying Rydberg excitations was usually made with the use of term values that are similar to those of the corresponding excitations in the molecules with analogous structures.t The frequencies of Rydberg bands are related to ionization potentials (IP), and their structures characterize the molecular and electronic structures of compounds. I Therefore, studies of Rydberg excitations in molecules of sandwich complexes provide valuable data on the effect of various factors on the ionization characteristics and mutual arrangement of electronic levels.Previously, z-9 it has been demonstrated that in the vapor-phase spectra of a number of alkyl-substituted derivatives of (q6-C6H6)2Cr (1), most of the bands correspond to Rydberg transitions from the 3dz~ orbital of the Cr atom. Introduction of methyl groups (from one to three) into each benzene ring of compound 1 results in a change in the ...

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Reduction of a permethylpentalene zirconium(iv) chloride complex [η-Pn*Zr(μ-Cl)](μ-Cl)Li·THF with KC in benzene results in activation of the aromatic solvent to yield an "inverted sandwich" complex, [η-Pn*Zr](μ-η:η-CH) (1). The reactions in toluene, cumene, o-xylene and m-xylene also yield analogous solvent activated triple-decker sandwich complexes, which have been structurally characterised by single-crystal X-ray diffraction. Edge energies in the Zr K-edge XANES spectra are not distinguishable between 1 and formally Zr(ii) and Zr(iv) reference compounds, suggesting a broad edge structure. DFT calculations best describe the bonding in 1 as highly covalent with frontier molecular orbitals showing almost equal contributions from benzene and the Zr-permethylpentalene fragments.