Derivatization\nof Undecahalogenated <i>closo</i>-Dodecaborates [B<sub>12</sub>X<sub>11</sub>NH<sub>3</sub>]<sup>−</sup> (X = F–I):\nAttaching Isocyanate, Amidinium, and Formamide\nFunctiona

Halogenated <i>closo</i>-dodecaborates are\nvery robust\nand versatile weakly coordinating anions for numerous applications.\nThe introduction of additional substituents, e.g., pseudohalides,\nallows the tuning of their chemical and physical properties. In this\nreport, the synthesis of the isocyanate-substituted <i>closo</i>-dodecaborates [B<sub>12</sub>X<sub>11</sub>(NCO)]<sup>2–</sup> (X = H, F–I) was investigated. In an attempt to synthesize\nthe undecahalogenated derivatives, a selective and halogen-dependent\nreaction yielding boron clusters carrying the functional groups amidinium\n(−NHCHNMe<sub>2</sub>) and formamide (−NHC(O)H) was\ndiscovered. The halogenated anions were fully characterized by vibrational\nand NMR spectroscopy, mass spectrometry, and X-ray diffraction. Salts\nof the formamide-substituted anion [B<sub>12</sub>X<sub>11</sub>(NHC(O)H)]<sup>2–</sup> are surprisingly thermally stable in the condensed\nphase. In contrast, collision-induced dissociation in the gas phase\nreveals that the isolated dianion [B<sub>12</sub>X<sub>11</sub>(NHC(O)H)]<sup>2–</sup> in the gas phase preferentially loses water, while\nthe protonated form, which was generated from decomposition of the\ntetraalkylammonium counterion [B<sub>12</sub>X<sub>11</sub>(NHC(O)H)H]<sup>−</sup>, tends to lose carbon monoxide. Possible reaction\nmechanisms are discussed.