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首页> 外文期刊>Zeitschrift fur Anorganische und Allgemeine Chemie >Reversible SO _2 uptake by tetraalkylammonium halides: Energetics and structural aspects of adduct formation between SO _2 and halide ions
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Reversible SO _2 uptake by tetraalkylammonium halides: Energetics and structural aspects of adduct formation between SO _2 and halide ions

机译：卤代四烷基铵可逆地吸收SO _2：SO _2与卤离子之间加合物形成的能级和结构方面

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摘要

Contact with SO _2 causes almost immediate dissolution of tetraalkylammonium halides, R _4NX, (R = CH _3 (Me), X = I; R = C _2H _5 (Et), X = Cl, Br, I; R = C _4H _9 (nBu), X = Cl, Br), with the formation of an adduct, [R _4N] ~+[(SO _2) _nX] ~- (n = 1-4). Vapor pressure measurements indicate the proclivity for SO _2 uptake follows the order N(CH _3) _4 ~+ < N(C _2H _5) _4 ~+ < N(C _4H _9) _4 ~+. This trend is in accord with the Jenkins-Passmore volume-based thermodynamic model. Born-Haber cycles, incorporating the lattice energy and gas phase energy terms, are used to evaluate the energetic feasibility of reactions. Density functional theory calculations (B3PW91; 6-311+G(3df)) have been used to calculate the energetics of (SO _2) _nX ~- (X = Cl and Br) anions in the gas phase. The experimental studies show that tetraalkylammonium halides are feasible sorbents for SO _2. In order to correlate the theoretical model, experimental enthalpy, Δ _rH° and entropy, Δ _rS° changes have been determined by the van't Hoff method for the binding of one SO _2 molecule to (C _2H _5) _4NCl, resulting in the liquid adduct (C _2H _5) _4NCl·SO _2. The structure of the analogous 1:1 bromide adduct, (C _2H _5) _4NBr·SO _2, has been determined by single-crystal X-ray diffraction (monoclinic, P2 _1/c, a = 9.1409(14) ?, b = 12.3790(19) ?, c = 11.3851(17) ?, β = 107.952(2)°, V = 1225.6(3) ? 3). The structure consists of discrete alkylammonium cations, bromide anions and SO _2 molecules with short contacts between the anion and SO _2 molecules. The (C _2H _5) _4N ~+ cationadopts a transoid conformation with D ~(2d) symmetry, and represents a rare example of a well-ordered (C _2H _5) _4N ~+ cation in a crystal structure. The Br ~- anions and SO _2 molecules forms a chain, (SO _2Br ~-) _n, with bifurcated contacts. Non-bonding electron pairs on the halide anions engage in electrostatic interactions with the sulfur atoms and charge-transfer interactions with the antibonding S-O orbitals of the bound SO _2 moiety. Raman and ~(17)O NMR spectra provide compelling evidence for a charge-transfer interaction between SO _2 molecules and the halide ions.
机译：与SO _2接触会导致四烷基卤化铵几乎立即溶解R _4NX（R = CH _3（Me），X = I; R = C _2H _5（Et），X = Cl，Br，I; R = C _4H _9 （nBu），X = Cl，Br），形成加合物[R _4N]〜+ [（SO _2）_nX]〜-（n = 1-4）。蒸气压测量表明SO _2吸收的倾向性遵循以下顺序：N（CH _3）_4〜+

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