[en] Cp(OC)₂ClW (2), Cp(OC)₂MeW (3); R = Et (a), Pr (b), Bu (c), Pe = Pentyl (d) and [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 the authors to estimate the quadrupolar coupling constant χ and the asymmetry parameter η of the electric field gradient at manganese

[en] The principal components of the carbon, nitrogen, and selenium chemical shift (CS) tensors for several solid selenocyanate salts have been determined by NMR measurements on stationary or slow magic-angle-spinning powder samples. Within experimental error, all three CS tensors are axially symmetric, consistent with the expected linear geometry of these anions. The spans (ω) of the carbon and selenium CS tensors for the selenocyanate anion (SeCN^-) are approximately 300 and 800 ppm, respectively, much less than the corresponding values for carbon diselenide (CSe₂). This difference is a consequence of the difference in the CS tensor components perpendicular to the C_∞ symmetry axes in these systems. Ab initio calculations show that the orbital symmetries of these compounds are a significant factor in the shielding. For CSe₂, efficient mixing of the sigma and pi orbitals results in a large paramagnetic contribution to the total shielding of the chemical shielding tensor components perpendicular to the molecular axis. Such mixing is less efficient for the SeCN^-, resulting in a smaller paramagnetic contribution and hence in greater shielding in directions perpendicular to the molecular axis. (author)