Synthetic Precursors for
TCNQF<sub>4</sub><sup>2–</sup> Compounds: Synthesis, Characterization,
and Electrochemical Studies
of (Pr<sub>4</sub>N)<sub>2</sub>TCNQF<sub>4</sub> and Li<sub>2</sub>TCNQF<sub>4</sub>
- Publication date
- Publisher
Abstract
Careful control of the reaction stoichiometry and conditions
enables
the synthesis of both LiTCNQF<sub>4</sub> and Li<sub>2</sub>TCNQF<sub>4</sub> to be achieved. Reaction of LiI with TCNQF<sub>4</sub>, in
a 4:1 molar ratio, in boiling acetonitrile yields Li<sub>2</sub>TCNQF<sub>4</sub>. However, deviation from this ratio or the reaction temperature
gives either LiTCNQF<sub>4</sub> or a mixture of Li<sub>2</sub>TCNQF<sub>4</sub> and LiTCNQF<sub>4</sub>. This is the first report of the
large-scale chemical synthesis of Li<sub>2</sub>TCNQF<sub>4</sub>.
Attempts to prepare a single crystal of Li<sub>2</sub>TCNQF<sub>4</sub> have been unsuccessful, although air-stable (Pr<sub>4</sub>N)<sub>2</sub>TCNQF<sub>4</sub> was obtained by mixing Pr<sub>4</sub>NBr
with Li<sub>2</sub>TCNQF<sub>4</sub> in aqueous solution. Pr<sub>4</sub>NTCNQF<sub>4</sub> was also obtained by reaction of LiTCNQF<sub>4</sub> with Pr<sub>4</sub>NBr in water. Li<sub>2</sub>TCNQF<sub>4</sub>, (Pr<sub>4</sub>N)<sub>2</sub>TCNQF<sub>4</sub>, and Pr<sub>4</sub>NTCNQF<sub>4</sub> have been characterized by UV–vis, FT-IR,
Raman, and NMR spectroscopy, high resolution electrospray ionization
mass spectrometry, and electrochemistry. The structures of single
crystals of (Pr<sub>4</sub>N)<sub>2</sub>TCNQF<sub>4</sub> and Pr<sub>4</sub>NTCNQF<sub>4</sub> have been determined by X-ray crystallography.
These TCNQF<sub>4</sub><sup>2–</sup> salts will provide useful
precursors for the synthesis of derivatives of the dianions