Hydrogen-Bonded Structures Formed from the Reaction of 1,3,5-Benzene-triphosphonic Acid and Adamantane
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The triphosphonic acid 1,3,5-benzene-triphosphonic acid (BTP; 1,3,5-[(HO)2PO]3C6H3) was allowed to react with different ratios of adamantane. Three compounds with amine to BTP ratios of 2:1, 4:1, and 6:1 were isolated, and their crystal structures were determined by single crystal X-ray diffraction. In the 2:1 compound the BTP molecules transferred two protons to the amines to form a complex of composition [C10H15NH3]22+[C 6H3(PO3H)2PO3H 2]2-·2H2O. This compound formed zig-zagged chains of BTP molecules hydrogen bonded to each other with the amine cations and water molecules interspersed between the chains. The 4:1 complex also formed chains through hydrogen bonding between the individual BTP molecules, but the chains are separated from each other by a double layer of protonated amines. In the 6:1 compound, all the protons are transferred to the adamantane molecules so that there is no hydrogen bonding between BTP molecules. Rather, a very complex hydrogen bond system between amine-BTP, amine-water and water-BTP results. In all three complexes, all the protonated amino groups hydrogen bond by utilizing all three of their protons as donors. The pK a values of the BTP protons were determined by analysis of the titration curve. © 2008 American Chemical Society.
author list (cited authors)
Kong, D., Yao, J., Clearfield, A., & Zon, J.