Alkoxy substituted halogenated closo-dodecaborates as anions for ionic liquids

Area of Science:

• Inorganic Chemistry
• Materials Science

Background:

• Closo-dodecaborates are versatile boron clusters with potential applications in various fields.
• Functionalization of closo-dodecaborates allows for tuning of their properties.

Purpose of the Study:

• To synthesize novel halogenated and alkoxylated closo-dodecaborate anions.
• To prepare and characterize their tetrabutylammonium and 1-hexyl-3-methylimidazolium salts.
• To investigate the thermal properties and potential ionic liquid behavior of these new compounds.

Main Methods:

• Synthesis via halogenation of [B12H11OH](2-) followed by alkylation in DMSO/KOH.
• Metathesis reactions to form tetrabutylammonium ([NBu4](+)) and 1-hexyl-3-methylimidazolium ([C6mim](+)) salts.
• Characterization using NMR, IR, Raman spectroscopy, ESI mass spectrometry, thermal analysis, and X-ray diffraction.

Main Results:

• Successful synthesis of halogenated and alkoxylated closo-dodecaborates [B12X11OR](2-).
• Formation of [NBu4](+) and [C6mim](+) salts, with [C6mim](+) salts showing thermal stability above 300 °C.
• The compound [C6mim]2[B12Cl11O-propyl] displayed a surprisingly low melting point of 96 °C.

Conclusions:

• The study presents a new class of functionalized closo-dodecaborates.
• The [C6mim](+) salts demonstrate good thermal stability.
• The discovery of [C6mim]2[B12Cl11O-propyl] as an ionic liquid highlights the potential for designing dianionic ionic liquids with tunable properties.