Structure of 1 : 1 and 1 : 2 complexes formed by aromatic NH and OH protondonors with aliphatic amines. Possibility of homoconjugated NHN+ cation formation

Structure of the complexes with NH . . .N hydrogen bond formed by bis(2,3,5 ,6-tetrafluoro-4-trifluoromethyl-phenyl)-amine ((4-CF3C6F4)(2)NH, FA) as pr oton donor with aliphatic amines (dibutyl-, tributyl- and trimethylamines) as proton accepters in aprotic solvents (isooctane and methylene chloride) in a wide range of concentrations and temperatures have been studied by LR and UV spectra. Quantitative treatment of the spectra by a computer program based on factor analysis reveals the equilibrium between free molecules an d FA-aliphatic amine complexes of 1:1 and 1:2 composition, the latter havin g an ionic structure with proton transferred from FA to the aliphatic amine . Thermodynamic characteristics of the 1:1 and 1.7 complexes for FA + dibut ylamine system have been measured. Appearance of LR bands indicating format ion of NHN+ homoconjugated cation has been detected in FA + trimethylamine solution in methylene chloride at temperatures 190-150 K. Spectral manifest ations of the complexes containing the (trimethylamine-H-trimethylamine) cation; formed by FA and OH proton donor (pentachlorophenol) are compared. (C) 2001 Elsevier Science B.V. All rights reserved.