title: Fixation of carbon dioxide and related small molecules by a bifunctional frustrated pyrazolylborane Lewis pair.
abstract: The bifunctional frustrated Lewis pair 1-[bis(pentafluorophenyl)boryl]-3,5-di-tert-butyl-1H-pyrazole (1) was employed for small molecule fixation by reaction with carbon dioxide, paraformaldehyde, tert-butyl isocyanate, tert-butyl isothiocyanate, methyl isothiocyanate and benzonitrile, affording the adducts 3-8 as zwitterionic, bicyclic boraheterocycles. Treatment of 1 with tert-butyl isocyanide gave the isocyanide-borane complex 9, whereas the zwitterionic alkynylborate 10 was formed by C-H bond activation of phenylacetylene. The molecular structures of all products 3-10 were established by X-ray diffraction analyses. DFT calculations at the M06-2X/6-311++G(d,p) level of theory revealed that CO(2) fixation by 1 and formation of the adduct 3 is strongly exothermic and proceeds with a low energy barrier of approximately 7.3 kcal mol(-1) via an intermediate van der Waals complex.
authors.affiliation: Institut für Anorganische und Analytische Chemie, Technische Universität Carolo-Wilhelmina, Hagenring 30, D-38106 Braunschweig, Germany.
authors.forename: Eileen
authors.initials: E
authors.lastname: Theuergarten
authors.forename: Janin
authors.initials: J
authors.lastname: Schlösser
authors.forename: Danny
authors.initials: D
authors.lastname: Schlüns
authors.forename: Matthias
authors.initials: M
authors.lastname: Freytag
authors.forename: Constantin G
authors.initials: CG
authors.lastname: Daniliuc
authors.forename: Peter G
authors.initials: PG
authors.lastname: Jones
authors.forename: Matthias
authors.initials: M
authors.lastname: Tamm