Synthetic Precursors for TCNQF42– Compounds: Synthesis, Characterization, and Electrochemical Studies of (Pr4N)2TCNQF4 and Li2TCNQF4

Careful control of the reaction stoichiometry and conditions enables the synthesis of both LiTCNQF4 and Li2TCNQF4 to be achieved. Reaction of LiI with TCNQF4, in a 4:1 molar ratio, in boiling acetonitrile yields Li2TCNQF4. However, deviation from this ratio or the reaction temperature gives either LiTCNQF4 or a mixture of Li2TCNQF4 and LiTCNQF4. This is the first report of the large-scale chemical synthesis of Li2TCNQF4. Attempts to prepare a single crystal of Li2TCNQF4 have been unsuccessful, although air-stable (Pr4N)2TCNQF4 was obtained by mixing Pr4NBr with Li2TCNQF4 in aqueous solution. Pr4NTCNQF4 was also obtained by reaction of LiTCNQF4 with Pr4NBr in water. Li2TCNQF4, (Pr4N)2TCNQF4, and Pr4NTCNQF4 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 (Pr4N)2TCNQF4 and Pr4NTCNQF4 have been determined by X-ray crystallography. These TCNQF42– salts will provide useful precursors for the synthesis of derivatives of the dianions.