Klaus Eichele Publication Abstracts 1991

The P-31 chemical shift tensors of cyclic and acyclic metal phosphine complexes of the type [M]PPh₂R ([M] = (OC)₄BrMn (1), Cp(OC)₂ClW (2), Cp(OC)₂MeW (3); R = Et (a), Pr (b), Bu (c), Pe = Pentyl (d)) and cyclic [M]PPh₂(CH₂)_n ([M] = (OC)₄Mn (4), Cp(OC)₂W (5), Cp(OC)₂Mo (6); n = 3 (b), 4 (c); [M] = (OC)₄MnSO₂ (7); n = 2 (b), 3 (c), 4 (d)) are determined by solid-state NMR techniques and correlated to structural features of the compounds. In general, the isotropic chemical shift in the solid state was found to be of the same order as the chemical shift in solution. There are differences in the tensor components due to structural changes for the manganese complexes 1. Different bond-weakening abilities of a ligand (trans influence) in complexes 2 and 3 cause a large change of only one tensor component, while the other components remain constant. A "crossover" of the center shielding tensor component and the low-field component is observed for the five- and six-membered rings 4b-7b and 4c-7c, respectively. ⁵⁵Mn- and ^95/97Mo-³¹P coupling constants have been observed that are not obtainable in solution. The different spacings within the multiplets of the ³¹P CP/MAS spectrum of the manganese complex 1d allows us to estimate the quadrupolar coupling constant χ and the asymmetry parameter η of the electric field gradient at manganese.