SOLVENT-DEPENDENT CO-59 NMR-STUDY OF [CO(EN)(3)]CL-3 AND CIS,TRANS-[CO-(EN)(2)(N-3)(2)]NO3

The linewidths and chemical shifts of the Co-59 NMR spectra of [Co(en) (3)](3+), cis-[Co(en)(2)(N-3)(2)](+), and trans-[Co(en)(2)(N-3)(2)](+) were measured at 5.87 T in water, methanol, propanediol-1,2-carbonate , dimethyl sulfoxide, N,N-dimethylacetamide, and hexamethylphosphorami de. The changes in linewidths in different solvents are attributed to ion-solvent interaction. Excellent correlations were established betwe en the square root of the viscosity-normalized linewidths and their re spective cobalt chemical shifts. It was also established that the coba lt chemical shifts and linewidths were sensitive to the electronic str ucture of the oxygen in the solvents. It is suggested that the origin of the electric-field gradient at cobalt arises from the distortion of the electronic structure through donor and acceptor interaction with solvent molecules. In other words, the Deverell electronic distortion model is favored over the electrostatic model. This conclusion is supp orted by good correlations of the cobalt-59 chemical shifts with the a cceptor number of the solvents. (C) 1994 Academic Press, Inc.