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A Super-Oxidized Radical Cationic Icosahedral Boron Cluster
Preprints are manuscripts made publicly available before they have been submitted for formal peer review and publication. They might contain new research findings or data. Preprints can be a draft or final version of an author's research but must not have been accepted for publication at the time of submission.
submitted on 23.05.2020 and posted on 26.05.2020by Julia M. Stauber, Josef Schwan, Xinglong Zhang, Jonathan C. Axtell, Dahee Jung, Brendon
J. McNicholas, Paul H. Oyala, Andrew
J. Martinolich, Jay R. Winkler, Kimberly A. See, Thomas Miller, Harry B. Gray, Alexander Spokoyny
While the icosahedral closo-[B12H12]2– cluster does not display reversible electrochemical behavior, perfunctionalization of this species via substitution of all twelve B–H vertices with alkoxy orbenzyloxy (OR) substituents engenders reversible redox chemistry, providing access to clusters in the dianionic,monoanionic, and neutral forms. Here, we evaluated the electrochemical behavior of the electron-rich B12(O-3-methylbutyl)12 (1) cluster and discovered that a new reversible redox event that gives rise to a fourth electronic state is accessible through one-electron oxidation of the neutral species. Chemical oxidation of 1 with [N(2,4-Br2C6H3)3]•+ afforded the isolable •+ cluster, which is the first example of an open-shell cationic B12 cluster in which the unpaired electron is proposed to be delocalized throughout the boron cluster core. The oxidation of 1 is also chemically reversible, where treatment of •+ with ferrocene resulted in its reduction back to 1. The identity of •+ is supported by EPR, UV-vis, multinuclear NMR (1H, 11B), and X-ray photoelectron spectroscopic characterization.