Multinuclear PGSE Diffusion and Overhauser NMR Studies on a Variety of Salts in THF Solution

1H, 19F, and 7Li pulsed gradient spin-echo (PGSE) NMR measurements for a series of salts are reported. The 7Li is shown to complement the 1H and 19F measurements; however, the use of higher concentrations (for the less-sensitive 7Li) can lead to aggregation. For all of the salts discussed {Li(BF4); (n-Bu4N)(BF4), a trinuclear Ru cluster; [Ir(1,5-COD)(4)](BF4), where 4 is a chiral P,N ligand; and the crown ether stabilized potassium salt, [K(18-crown-6)(NPh2)], 6}, the use of THF seems to promote strong ion pairing. In several cases, the degree of ion pairing approaches 100%. In THF solution, the potassium salt, 6, prefers to exist as a more classical ion pair rather than as the (pi)complex found in the solid state. In some cases, 1H, 1H NOESY and 1H, 19F HOESY spectra help to pinpoint the cation/anion spatial relationship.