title: The R3O+···H+ hydrogen bond: toward a tetracoordinate oxadionium(2+) ion.
abstract: Oxatriquinanes are tricyclic oxonium ions which are known to possess remarkable solvolytic stability compared to simple alkyl oxonium salts. Their rigid, hemispherical structure presents an oxygen at the apex of three fused five-membered rings. While trivalent oxygen species like these have been well described in the literature, the ability of oxygen to enter into a fourth covalent bonding relationship has been visited in theory and suggested by the outcome of certain reactions conducted in superacidic media, but has never been established by the characterization of a stable, persistent R(3)OH(2+) or R(4)O(2+) ion. In this study, the nucleophilicity of the oxatriquinane oxygen was evaluated first by a series of protonation studies using the Brønsted superacid H(CHB(11)Cl(11)) both in the solid state and in liquid HCl solution. The interaction of the oxatriquinane oxygen with a bridging carbocation was also examined. A strong case could be made for the occurrence of hydrogen bonding between H(CHB(11)Cl(11)) and oxatriquinane using IR spectroscopy. Under the most forcing protonation conditions, the oxatriquinane ring is cleaved to give a bridged, dicationic, protonated tetrahydrofuran-carbenium ion.
authors: Department of Chemistry, University of California Riverside, 900 University Avenue, Riverside, California 92521-0403, USA. evgeniis@ucr.edu
authors: Evgenii S
authors: ES
authors: Stoyanov
authors: Gorkem
authors: G
authors: Gunbas
authors: Nema
authors: N
authors: Hafezi
authors: Mark
authors: M
authors: Mascal
authors: Irini V
authors: IV
authors: Stoyanova
authors: Fook S
authors: FS
authors: Tham
authors: Christopher A
authors: CA
authors: Reed
mesh_terms: D000478:Alkylation; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008968:Molecular Conformation; D010100:Oxygen / Q000737:chemistry*; D011522:Protons
chemical_list: D011522:Protons; D010100:Oxygen