Spectroscopic studies carried out on [Co(dmgBF2)2(H2O)2] (where dmgBF2 = difluoroboryldimethylglyoximato) in the presence of triethylamine in acetonitrile, provided strong evidence that there was an interaction between the cobalt(II) metal center and triethylamine, a reaction has not been in the literature. In the UV-visible spectrum, two peaks circa 560 and 650 nm generally associated with the formation of cobalt(I) species were observed, and formed within minutes, and their rates of formation displayed a dependence on the concentration of triethylamine. Preliminary kinetic studies on this system indicated an initial absorbance change of the peak circa 330 nm, which most likely involved the substitution of an axial solvent molecule by triethylamine prior to an electron transfer process. From an ESI MS study in the positive mode, there was evidence of the formation of a transient species, which corresponded to [Co(dmgBF2)2(NEt3)(NCCH3)]. In the presence of triethylamine, cyclic voltammograms in acetonitrile also showed a time dependent decrease in the peak current associated with the CoII/I redox couple, and a simultaneous alteration of the potential of CoI/0 redox couple. A 1H NMR spectroscopic time course study in CD3CN further revealed a time dependent shift downfield from 2.17 to 2.22 ppm of the methyl peaks of the dmgBF2 ligand; consistent with changes electron density on the metal center. In conclusion, it was theorized that the triethylamine substituted one of the solvent molecule in the axial position on the cobaloxime, followed by an electron transfer from triethylamine to the cobalt(II) metal center.

Overlooked reaction involving a catalyst, [Co(dmgBF2)2(OH2)2], and a sacrificial electron donor, triethylamine during the production of hydrogen in acidified acetonitrile: A mechanistic study that must not be ignored!

251st National Meeting (2016)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.