Synthesis, Electronic Properties and Reactivity of [B X (NO )] (X=F-I) Dianions.

Nitro-functionalized undecahalogenated closo-dodecaborates [B X (NO )] 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 substituent leads to an enhanced electronic and electrochemical stability compared to the parent perhalogenated [B X ] (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 X O] . Theoretical investigations suggest that the loss of NO proceeds via the rearrangement product [B X (ONO)] . The O-bonded nitrosooxy structure is thermodynamically more stable than the N-bonded nitro structure and its formation by radical recombination of [B X O] and NO is demonstrated.