Akira Yamasaki

Nuclear magnetic resonance studies on cobalt complexes. I. Cobalt-59 nuclear magnetic resonance spectra of cobalt(III) complexes.

Abstract Cobalt-59 NMR spectra were recorded for forty tervalent diamagnetic cobalt complexes. The chemical shift and line width were briefly discussed using Ramseys expression and assuming quadrupolar interaction. The chemical shift is correlated with the total electronegativity of all ligand atoms and radial factors. As to chemical shift data, Ramseys formula can be applied when proper consideration of the radial factor is given. Comments are given on earlier chemical shift data.

NMR studies of cobalt complexes. Theoretical interpretation of cobalt-59 chemical shifts

Abstract A theoretical interpretation of cobalt-59 chemical shifts is carried out using a molecular orbital treatment. It is shown that the chemical shifts of several complexes which contain sulfur as ligands can be interpreted with the introduction of an orbital reduction factor, k′, and a radial factor, l 1 r 3 〉 c . Also, the absolute value of the gyromagnetic ratio, γ0, of cobalt-59 is estimated as (6.2928±0.0010) × 103 G−1 sec−1 from a graphical presentation of the data. The absolute chemical shift, i.e. the chemical shift from γ0 of cobalt-59 in hexacyanocobaltate(III), which is the compound generally adopted as the standard material, is obtained as 1.10%.

Thermal Motion of Ammine Groups in Carbonatotetrammine Cobalt (III) by Proton Nuclear Magnetic Resonance

The broad-line NMR spectra of carbonatotetramminecobalt (III) bromide were observed in polycrystalline state at temperatures between 77°K and 383°K. It has been concluded that 1) from 200°K to 383°K the ammine groups are rotating about the Co-N axis, 2) there is no motion of the complex cation as a whole up to the decomposition point, and 3) below 90°K one of the four ammine groups in each complex becomes stationary.