Structure of 1,3-xylyl-(18-crown-5)–ammonium catecholborate (1/1)

Abstract

REGULAR STRUCTURAL PAPERSCrystals were obtained from methanol solution by slow evaporation. A parallelepiped crystal fragment was cut from a larger crystal and mounted in a Lindemann capillary to prevent its sublimation. _Dt~_ g the data collection intensifies of the standard reflections (221,004 and 400) dropped by up to 89% of their initial values. Data were corrected for crystal decay.We thank Professor Herbert Mayr, Technische Hochschule Darmstadt, for synthetic hints.Lists of structure factors, anisotropic thermal parameters, H-atom coordinates, torsion angles and ring-puckering parameters have been deposited with the British Library Document Supply Centre as Supplementary Publication No. SUP 55627 (28 pp.). Copies may be obtained through The Technical Editor, International Union of Crystallography, 5 Abbey Square, Chester CH1 2HU, England. [CIF reference: AB 1017] References Cremer, D. & Pople, J. A. (1975). J. Am. Chem. Soc. 97, 1354-1358. Ilczyszyn, M. M., Lis, T., Baran, J. & Ratajczak, H. (1992). J. Mol. Struct. 265, 293-310. Johnson, C. K. (1976 L2=o oThe results of the structure analysis are summarized in Fig. 1 which shows an ion-pair complex comprising ammonium catecholborate attached to a macrocyclic crown ether. The ammonium cation is bonded on one side by three hydrogen bonds to a 1,3-xylyl-(18-crown-5) polyether and on the other through a single hydrogen bond to a catecholborate anion. Interestingly, the ammonium cation forms hydrogen bonds preferentially with the O atoms of the crown ether in spite of the fact that the catecholborate anion is negatively charged and carries four O atoms that are eminently suited to form hydrogen bonds. By way of comparison, ammonium tetrafluoroborate crystallizes as a three-dimensional structure with each H atom of the ammonium cation hydrogen bonded, albeit weakly (Pendred & Richards, 1955), to an F atom of a neighbouring tetrafluoroborate anion (Clark & Lynton, 1969; Van Rensburg & Boeyens, 1972;Stromme, 1974 LSCELD (Davis, 1969 AbstractThe host molecule lies on the crystallographic twofold axis. The centroid of the guest, p-xylene, is located at a center of symmetry. The host forms a cage-type 1" 1 clathrate with p-xylene. The p-xylene is

Synthesis and Biological Activities of Arylspiroborates Derived from 2,3‐Dihydroxynaphthalene

“…and crystallographic data provided in Table . Bond distances and angles are similar to those reported in related arylspiroborate compounds . As expected, the cyclic ring structure induces a contraction of the O–B–O angles in the five‐membered rings, with O(1)–B(1)–O(2) 104.59(15) o and O(3)–B(1)–O(4) 104.86(15) o .…”

Is the Formation of Poly-CO2 Stabilized by Lewis Base Moieties in N- and S-Doped Porous Carbon?

“…In contrast, H + shows a significant structural effect on both the 1st and 2nd CO2, with diminishing results with distance (Table 1, Figure 5c). Again, as with AlF3 the more stable form involves the H + hydrogen bonding between two CO2 molecules, with the O … O distance (2.410 Å) being typical of an O-H … O hydrogen bond [23,24]. From the proceeding it is clear that Lewis acid species have a similar effect on the stabilization of oligomeric CO2 that is observed with Lewis bases.…”

“…. O hydrogen bond [23,24]. Initially, structural optimization was undertaken for the LA stabilized CO2 tetramer ( Figure 2b).…”

Determination of the mode and efficacy of the cross-linking of guar by borate using MAS11B NMR of borate cross-linked guar in combination with solution11B NMR of model systems

“…Examples of borate complexes derived from monodentate alcohols, [B(OR) 4 ] − , are well known, although only a few have been structurally characterized, and they are generally prepared from non-aqueous solution. [12][13][14] Given the chelate effect, it is more likely that any cross-linking involves bidentate coordination of a 1,2 or 1,3 diol. Although tridentate coordination is known for 1,3,5-triols 15 Although the residual boric acid resonance is pH dependent, the peaks due to the diol complexes are pH independent (e.g., Fig.…”

“…( 2) as a model reaction, the cross-linking of guar (G) can be represented by the equilibria shown in eqn. (14).…”