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Unwrapping the Dodecaborane Core: Structure, Electronic Properties, and Chemical Reactivity Across the Complete [B 12 I n ] − Series ( n = 11–1)

Year: 2026

Type: article

Abstract: High Resolution Image Download MS PowerPoint Slide Successively stripping the exohedral substituents from the stable closo -dodecaborate anion [B 12 I 12 ] 2– results in structural transformations of the icosahedral B 12 into a (quasi-)planar unsubstituted B 12 unit. Previous studies have revealed that [B 12 I 11 ] − to [B 12 I 8 ] − ions contain a closed B 12 unit, while [B 12 I 7 ] − is the first ion in the series with an opened B 12 unit. Further transitions in geometry, electronic structure, and chemical reactivity across the whole range of fragments [B 12 I n ] − ( n = 11–1) remain elusive. Herein, we report a systematic investigation to explore the chemical properties of these intermediate structures by using negative ion photoelectron spectroscopy (NIPES), ion mobility spectrometry (IMS), gas-phase ion–molecule reactions, and quantum chemical calculations. [B 12 I n ] − ions can be categorized into three groups: (1) very reactive ions with intact (quasi-)icosahedral B 12 cages ( n = 11–8), (2) less reactive ions with open structures ( n = 7–4), and (3) almost unreactive ions with (quasi-)planar structures ( n = 3–1). Preparative mass spectrometry shows that ions with the unsaturated B 12 core (category 2) tend to form smaller, fully substituted closo -borate anions [B m X m ] 2– ( m = 6–11 with X = I, H, OH) on surfaces. In contrast, ions in category 3 cannot be found on the surface and apparently decay into volatile products. This research provides fundamental insights into the physical and chemical properties of B 12 units depending on their substitution level and paves the way for the rational design of boron-rich compounds by using unconventional [B 12 I n ] − building blocks.

Source: Journal of the American Chemical Society

DOI: 10.1021/jacs.6c04725