The isotropic contact NMR shifts of the coordinated cis and tram methanol methyl proton resonances of a series of Co(CH30H)5X2+ complexes were measured, where the ligand X was pyridine, /I- and a-picoline, DMF, DMSO, acetonitrile, and water. The question of how to separate the observed shifts into their respective Fermi contact and dipolar (pseudocontact) contributions was examined in detail with the result that a new procedure for carrying out the separation was proposed. The dipolar shifts for these complexes were found to vary widely, with the acetonitrile complex exhibiting the largest dipolar shift. For the DMSO and water complexes the sign of the dipolar shift was reversed relative to the others. Qualitatively this sign reversal may be related to the difference in ligand field strengths of methanol and X relative to the spin orbit soupling constant for cobalt (II). It was also concluded that the Fermi contact shift varied between complexes.
Vriesenga, J. R., & Goodisman, J. (1975). Methyl proton NMR shifts of coordinated methanol in a series of co(CH3OH)5X2+ compounds. Journal of Magnetic Resonance (1969), 20(1), 102-109.
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