Host-guest complexes of 18-crown-6 with neutral molecules possessing the structure element XH2 (X = oxygen, nitrogen, or carbon)

Can. J. Chem. 67, 32 (1989). The macrocyclic polyether 18-crown-6 forms complexes with hydrates of strong acids derived from transition metal chlorides and hydrochloric acid. The following charged-component complexes have been isolated and characterized:18-crown-6. H 3 0 + . FeC14-, 18-crown-6. H30+ . InC14-, and (18-crown-6. H30+)2. pd2Cls2-. X-ray diffraction study of the palladium complex is reported. The oxonium ion is located at the center of the macrocyclic ether cavity and the symmetry of the ring is close to D3d.

Section: Introductionmentioning

confidence: 99%

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⁻

Chênevert¹,

Chamberland²,

Simard³

et al. 1989

“…A particularly good example of this is found in the CH,(CN)COOH.H20. 18C6 adduct, whose crystal and molecular structures have been determined by X-ray diffraction (3). Also of interest is the corresponding compound of 2:2: 1 stoichiometry obtained from dichloropicric acid, in which proton transfer seems to occur from theacid to water, giving a charged-component complex involving the hydronium ion (4).…”

Section: Introductionmentioning

confidence: 99%

Synthesis, crystal and molecular structure, and vibrational spectra of the complex (COOH)₂•2H₂O•18-crown-6

Deguire¹,

Brisse²,

Ouellet³

et al. 1986

. Can. J. Chem. 64, 142 (1986). A stoichiometric complex of formula (COOH)2.2H2018-crown-6 has been obtained from oxalic acid and the macrocyclic polyether 18-crown-6. The crystals of the complex have a monoclinic unit cell and belong to the P2,/c space group. The components in the adduct are linked through hydrogen bonds in a polymer-like fashion: -crown-H20-HOOCCOOH-OH2-crown-, where the oxalic acid molecules are present in two distinct disordered orientations. The infrared and Raman spectra of the complex are also reported and interpreted.

“…4). When the crown possesses D,,, or approximately D,,, symmetry, as in unheated 1 : 1 : 1 and 1 : 2: 2 aqua complexes of 18-cr-6 with phenols or carboxylic acids, the C-0-C, C-C stretching, and CH2-CH, rocking mode bands occurring at -1 110, -835, and -960 cm-I are not, or only slightly, split (19)(20)(21). This is found with adducts 1, 2, and 2D in this study (Table 3).…”

Section: Ir Spectra Of Adductsmentioning

confidence: 99%

Binding of water in aqua 18-crown-6 dichloropicric acid complexes in the solid state and its reversible thermal removal

Kolthoff¹,

Chantooni²

1992

Can. J. Chem. 70, 177 (1992). Thermogravimetry, differential scanning calorimetry, and FT-IR vibrational spectral studies on the 1 : 1 : 1 18-crown-6:dichloropicric acid:water complex reveal that it remains unaltered when heated to melting. On the other hand, one molecule of water is expelled from the 1 : 2 : 2 complex by heating prior to melting. This results in an ionic microcrystalline product of undetermined crystal structure, in which the conformation of the crown is lower than D,, in symmetry. The enthalpy accompanying this process, which involves rupturing of two water-crown hydrogen bonds, is -44 to -55 kJ mol-I. The original 1 : 2 : 2 complex is regenerated by exposure of the heated adduct to water vapor. It was found that H,O in the structure of the solid 1 : 2: 2 adduct was partially replaced by D,O at room temperature upon exposure to D 2 0 vapor. The crown-H,O OH stretch in the IR exhibits a small or negligible positive isotope effect on deuteration.Key words: crown ether, hydrogen bonding, water, dichloropicric acid.