title: Carbon monoxide protonation in condensed phases and bonding to surface superacidic Brønsted centers.
abstract: Using infrared (IR) spectroscopy and density functional theory (DFT) calculations, interaction of CO with the strongest known pure Brønsted carborane superacids, H(CHB11Hal11) (Hal = F, Cl), was studied. CO readily interacted at room temperature with H(CHB11F11) acid, forming a mixture of bulk salts of formyl and isoformyl cations, which were in equilibrium An(-)H(+)CO COH(+)An(-). The bonding of CO to the surface Brønsted centers of the weaker acid, H(CHB11Cl11), resulted in breaking of the bridged H-bonds of the acid polymers without proton transfer (PT) to CO. The binding occurred via the C atom (blue shift ΔνCO up to +155-167 cm(-1), without PT) or via O atom (red shift ΔνCO up to -110 cm(-1), without PT) always simultaneously, regardless of whether H(+) is transferred to CO. IR spectra of all species were interpreted by B3LYP/cc-pVQZ calculations of the simple models, which adequately mimic the ability of carborane acids to form LH(+)CO, LH(+)CO, COH(+)L, and COH(+)L compounds (L = bases). The CO bond in all compounds was triple. Acidic strength of the Brønsted centers of commonly used acid catalysts, even so-called superacidic catalysts, is not sufficient for the formation of the compounds studied.
authors.affiliation: Vorozhtsov Institute of Organic Chemistry, Siberian Branch of Russian Academy of Sciences (SB RAS), Novosibirsk 630090, Russia. evgenii@nioch.nsc.ru and Department of Natural Science, National Research University - Novosibirsk State University, Novosibirsk 630090, Russia.
authors.forename: Evgenii S
authors.initials: ES
authors.lastname: Stoyanov
authors.affiliation: Department of Natural Science, National Research University - Novosibirsk State University, Novosibirsk 630090, Russia and Boreskov Institute of Catalysis SB RAS, Novosibirsk 630090, Russia.
authors.forename: Sergei E
authors.initials: SE
authors.lastname: Malykhin