Abstract
The ion pairing interaction in [(n-C4H9)4N][(C6H5)3PCoBr3] has been studied by proton magnetic resonance spectroscopy in a series of different solvents. The observed paramagnetic resonance shifts of the N-methylene protons of the ammonium ion were determined for a 0.058 M solution in nine different solvents with the dielectric constant ranging from 4.65 to 64.2. By concentration vs. chemical shift studies, the concentration association constants and the isotropic resonance shifts of the N-methylene protons in the fully ion-paired species were determined in each of the following solvents: o- and m-nitrotoluenes, nitrobenzene, and propylene carbonate. The concentration association constants were found to be constant over a concentration range of 0.02-0.5 M in electrolyte and to increase with a decrease in dielectric constant of the solvent. This finding is used to challenge the common procedure of making activity corrections to spectrophotometric data. The N-methylene proton isotropic resonance shifts of the fully ion-paired species were the same within experimental error in the former three solvents and smaller in propylene carbonate. The smaller shift in propylene carbonate (e = 63.0) was interpreted to indicate a longer interionic distance for the ion pair in the higher dielectric solvent.
Original language | English |
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Pages (from-to) | 84-90 |
Number of pages | 7 |
Journal | Journal of the American Chemical Society |
Volume | 94 |
Issue number | 1 |
DOIs | |
Publication status | Published - 1 Jan 1972 |
Externally published | Yes |