SYNTHESES, PROPERTIES, AND STRUCTURES OF ANHYDROUS TETRAMETHYLAMMONIUM FLUORIDE AND ITS 1-1 ADDUCT WITH TRANS-3-AMINO-2-BUTENENITRILE

A simple method for the preparation of anhydrous and essentially HF2 --free N(CH3)4F is described. The compound was characterized by X-ray diffraction, NMR, infrared, and Raman spectroscopy. It crystallizes in the hexagonal system with a hexagonal closest packing of the N(CH3)4 +cations. It is shown that the free F-anion is a very strong Lewis base and chemically reacts with most of the solvents, such as CH3CN or chlorinated hydrocarbons, previously used for studies of the fluoride anion. As a result, some of the properties previously reported for F-were due to HF2 -or other secondary reaction products. Its relatively simple synthesis and lower cost, combined with its good solubility and the high chemical inertness of the N(CH3)4 +cation, make N(CH3)4F an excellent substitute for presently used fluoride ion sources, such as either [(CH3)2N]3S+F2Si(CH3)3-, which is commonly referred to as tris(dimethylamino)sulfonium fluoride, or CsF. The reaction of N(CH3)4F with CH3CN results in the dimerization of CH3CN and the formation of a 1:1 adduct of N(CH3)4F with this dimer, trans-3-amino-2-butenenitrile. The crystal structure and vibrational spectra of this adduct are reported. © 1990, American Chemical Society. All rights reserved.