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.