Weakly Coordinating yet Ion Paired: Anion Effects on an Internal Rearrangement
Professor Aaron Odom and co-workers have recently published an article in Organometallics which has been chosen for highlighting on the cover of the April 10, 2017 issue.
One of the most important interactions in chemistry, and perhaps one of the most ignored, are outer-sphere anion-cation ion pairing effects. Using a Cr(VI)-based system, they explored the effects of ancillary ligands on an internal rearrangement. For cationic systems (lavender puzzle pieces in figure), it was found that the nature of the anion could contribute strongly. In some cases, relatively small anions like PF6— and SbF6— (yellow and green puzzle pieces) seem to bind in a very specific site to the cation, which happens to affect the rearrangement being studied. The “weakly coordinating” tetraarylborates (BArF—, yellow disks) are just as ion paired as the smaller anions but are nonspecific in their binding to the cation, which leads to smaller effects on the rearrangement.
Their article is:
Kelly E. Aldrich, Brennan S. Billow, Daniel Holmes,
Ross D. Bemowski, and Aaron L. Odom