Synthesis and vibrational study of a 1:1 stoichiometric complex of hydronium tetrafluoroborate and 1,4,7,10,13,16-hexaoxacyclooctadecane (18-crown-6)

Abstract

. Can. J. Chem. 60,853 (1982). The macrocyclic ether 1,4,7,10,13,16-hexaoxaoctadecane (18-crown-6) has the remarkable property of being able to transfer the hydronium (H,O+) ion from an aqueous solution to an organic medium. This property has been used to synthetize a 1:l stoichiometric complex of this ether with hydronium tetrafluoroborate. This complex is very stable (mp 145°C) and dissolves readily, without decomposition, in solvents such as CHCI,. The presence of the H 3 0 + and BF4-ions in the complex has been confirmed by chemical analysis, and by IH nmr, Raman, and ir spectroscopy. The vibrational spectraindicate that a conformational change of the crown ether takes place in the complex over the temperature range -50°C to -100°C. The symmetry of the crown ether, which appears to be relatively high at room temperature, is considerably reduced below the transition temperature.ROBERT CH~NEVERT, AND& RODRIGUE, MARIE PIGEON-GOSSELIN et RODRIGUE SAVOIE. Can. J. Chem. 60,853 (1982). L'ether macrocyclique 1,4,7,10,13,16-hexaoxaoctad&cane (18-crown-6)

Complexes of 18-crown-6 with oxonium ions derived from transition metal chlorides and hydrochloric acid: 18-crown-6.H3O+. FeCl4−, 18-crown-6.H3O+.InCl4−, (18-crown-6.H3O+)2.Pd2Cl62−

“…The analyses are in agreement with the stoichiometries defined by reactions [I.] and [2] and with that observed in the X-ray determination for the palladium complex.…”

“…This type of complexation was first observed for the cis-syn-cis-dicyclohexano-18-crown-6 with H30+C104-or H30+PF6- (1). In recent years, it has been shown that 18-crown-6 is a good complexing agent for the hydronium ion, and complexes have been obtained with several strong acids (2)(3)(4)(5)(6)(7). In these studies, it was generally assumed that the H30+ ion in the adduct is located at the center of the macrocyclic ether cavity, as this would maximize the electrostatic interactions between the two units.…”

Synthesis and vibrational spectra of 1:1 stoichiometric complexes of nitronium and nitrosonium tetrafluoroborate with 18-crown-6

“…This rctlects the instability of the complex, particularly towards moisturc. Although the analysis suggests an incomplete complexation between NOIBF, and 18C6, the Raman spectrum of the solid complex, which is discussed below, gives no evidence for the presence of uncomplexed 18C6, whose spectrum is vcry characteristic (4). For the infrared, hexachlorobutadienc.…”

“…Both complexes can be hydrolyzcd to the corresponding hydronium conlplex, H30'BF,-. 18C6 (4). with a >95% yield.…”

“…We have recently reported on the synthesis and vibrational spectra of such a complex, H 3 0 ' BF,-. 18C6' (4), whose crystal structure is now being examined by X-ray cry~tallography.~…”