title: An ab initio and cryospectroscopic study of the hydrogen chloride and boron trifluoride complexes of cyclopropene.
abstract: Mid-infrared spectra of cyclopropene (c-C3H4) mixtures with HCl or BF3, dissolved in liquefied argon and in liquefied nitrogen have been examined. Evidence was found for the formation of two different isomers of the 1:1 complexes: a pi-type complex in which the interaction occurs with the pi-bond of cyclopropene, and a sigma-type complex in which the electron acceptors interact with one of the CC single bonds. At lower temperatures, indications for the formation of a 1:2 chain-type complex were found. Using spectra recorded between 90 and 124 K in liquid argon, the complexation enthalpies for the pi- and sigma-complexes with HCl were determined to be -8.8(3) and -7.9(3) kJ mol-1, respectively. For the pi-complex with BF3 a value of -7.4(3)kJ mol-1 was found. Structural and spectral information on the 1:1 complexes was obtained from B3LYP/6-311++G(d,p) and MP2(FC)/6-31+G(d) calculations. Using Free Energy Perturbation Monte Carlo simulations to calculate the solvent influences, and statistical thermodynamics to account for zero-point vibrational and thermal contributions, the solution enthalpies were transformed into complexation energies with values of -15.5(6) and -13.8(8) kJ mol-1 for the pi- and sigma-isomers of c-C3H4.HCl, respectively, and of -12.7(8) kJ mol-1 for the pi-type BF3 complex.
authors.affiliation: Department of Chemistry, University of Antwerp, Groenenborgerlaan 171, B2020 Antwerp, Belgium.
authors.forename: Gert P
authors.initials: GP
authors.lastname: Everaert
authors.forename: Wouter A
authors.initials: WA
authors.lastname: Herrebout
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: van der Veken
mesh_terms: D001128:Argon / Q000737:chemistry; D001880:Boranes / Q000737:chemistry*; D002244:Carbon / Q000737:chemistry; D003521:Cyclopropanes / Q000737:chemistry*; D006358:Hot Temperature; D006851:Hydrochloric Acid / Q000737:chemistry*; D008968:Molecular Conformation; D009010:Monte Carlo Method; D009584:Nitrogen / Q000737:chemistry; D013053:Spectrophotometry / Q000379:methods*; D013055:Spectrophotometry, Infrared; D013696:Temperature; D013816:Thermodynamics
chemical_list: D001880:Boranes; D003521:Cyclopropanes; D001128:Argon; D002244:Carbon; C021985:cyclopropene; C021274:boron trifluoride; D009584:Nitrogen; D006851:Hydrochloric Acid