A Super-Oxidized Radical Cationic Icosahedral Boron Cluster

Abstract

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[1] •+ 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 [1]•+ with ferrocene resulted in its reduction back to 1. The identity of [1]•+ is supported by EPR, UV-vis, multinuclear NMR (1H, 11B), and X-ray photoelectron spectroscopic characterization.<br>

Access to cationic polyhedral carboranes via dynamic cage surgery with N-heterocyclic carbenes

“…This is only achievable by an increase in the negative charge or the addition of bridging hydrogen atoms. At the same time, the number of the SEPs for monocationic clusters is likely to be different, n + 0.5 for closo up to n + 3.5 for hypho , but the cationic clusters are still elusive, except for closo -B 12 (3-methylbutyl) 12 + radical cation published very recently by Spokoyny 29 . There is a big number of cationic boranes, however, the positive charge is predominantly located on a functional group connected to the parent borane (Me 2 S 30 , phosphonium 31 and ammonium 32 ), not in the borane cage itself.…”