Synthesis, Electronic Properties and Reactivity of [B 12 X 11 (NO 2 )] 2− (X=F–I) Dianions

Nitro‐functionalized undecahalogenated closo ‐dodecaborates [B 12 X 11 (NO 2 )] 2− were synthesized in high purities and characterized by NMR, IR, and Raman spectroscopy, single crystal X‐diffraction, mass spectrometry, and gas‐phase ion vibrational spectroscopy. The NO 2 substituent leads to an enhanced electronic and electrochemical stability compared to the parent perhalogenated [B 12 X 12 ] 2− (X=F–I) dianions evidenced by photoelectron spectroscopy, cyclic voltammetry, and quantum‐chemical calculations. The stabilizing effect decreases from X=F to X=I. Thermogravimetric measurements of the salts indicate the loss of the nitric oxide radical (NO . ). The homolytic NO . elimination from the dianion under very soft collisional excitation in gas‐phase ion experiments results in the formation of the radical [B 12 X 11 O] 2−. . Theoretical investigations suggest that the loss of NO . proceeds via the rearrangement product [B 12 X 11 (ONO)] 2− . The O ‐bonded nitrosooxy structure is thermodynamically more stable than the N ‐bonded nitro structure and its formation by radical recombination of [B 12 X 11 O] 2−. and NO . is demonstrated.