Gehinderte ligandenbewegungen in übergangsmetallkomplexen : V. 1H-NMR-untersuchung der bewegungen des olefinliganden in cyclopentadienyl-mangan-dicarbonyl-tetramethoxyäthylen

The methoxy signals in the ¹H NMR spectrum of cyclopentadienylmanganese dicarbonyl tetramethoxyethylene, C₅H₅Mn(CO)₂[C₂(OCH₃)₄], show a definite temperature-dependence. In CS₂ solution the variations of the signals are observed within a single temperature range, while in toluene-d₈ two regions of change are found to exist. These data are explained on the basis of two mutually independent ligand movements: a hindered rotation of the olefin ligand around the metalligand bond (ΔG³₁₉₄ = 9.8 ± 0.6 kcal/mol), and a hindered movement of the four methoxy groups (ΔG³₂₆₃ = 13.8 ± 0.3 kcal/mol, both in toluene-d₈. Chiral conformations of the ligand are assumed to be formed when the movement of the methoxy substituents ceases.     

The size and equation of state of an athermal polymer in a strong solution: A screened convolution approximation

The configurational and thermodynamic properties of an athermal polymer system are determined at intermediate to high concentrations.     

Dispersion dynamics of crystal lattices

A new formalism is presented, which has not the difficulties of the conventionalGreen's function methods for disturbed lattice dynamics. The new method introduces aGreen's function and an eigenvector-function, which are defined in the wholeω-plane. A simple device allows to extract the conventional eigenvectors and eigenfrequencies from the eigenvector-function. AGreen's function formalism and a random-phase assumption make it possible to calculate the disturbed eigenvector-function from the undisturbed one in such a way that both are normalized to the respective density of frequencies. The formalism thus is well-fit to describe changes of the density of frequencies, shifts of the bands and discrete (localized) solutions outside the bands. Applicability to the elastic continuum and quantum mechanics seem also possible.