title: Fragmentation of Cr(NO3)4(-): Metal Oxidation upon O(•-) Abstraction.
abstract: The decomposition of chromium nitrate anion, Cr(NO3)4(-), was investigated by tandem mass spectrometry. The major fragments correspond to sequential elimination of NO2(•) via O(•-) abstraction from each nitrate ligand to yield CrOn(NO3)(4-n)(-), n = 1-4, products. The metal is oxidized upon the first three O(•-) abstraction reactions to yield the fully oxidized Cr(VI), closed-shell, CrO3(NO3)(-) fragment. A CrO4(-) fragment was detected, but the metal is not further oxidized upon the fourth O(•-) abstraction. Experiment and theory indicate the first three O(•-) abstraction reactions are low energy processes, but the formation of CrO4(-) is considerably higher in energy. Theoretical studies show the 3d electrons in chromium are removed by O(•-) for CrOn(NO3)(4-n)(-), n = 1-3, to yield oxo, O(2-) ligands, but the electron density is replaced by donation from π bonds involving the oxygen lone pairs. Theory predicts a decrease in metal charge for each O(•-) abstraction, opposite the trend expected for oxidation, due to π electron donation from the oxygen atoms.
authors.affiliation: Department of Chemistry, The University of Alabama , Tuscaloosa, Alabama 35487, United States.
authors.forename: Rachael M
authors.initials: RM
authors.lastname: Albury
authors.affiliation: Department of Chemistry, The University of Alabama , Tuscaloosa, Alabama 35487, United States.
authors.forename: Carrie Jo M
authors.initials: CJ
authors.lastname: Pruitt
authors.affiliation: Department of Chemistry, The University of Alabama , Tuscaloosa, Alabama 35487, United States.
authors.forename: Thomas H
authors.initials: TH
authors.lastname: Hester
authors.affiliation: Department of Chemistry, The University of Alabama , Tuscaloosa, Alabama 35487, United States.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Goebbert