Synthesis and structure of a product of interaction of acetonitrile with hydrogen bromide, [H2N=C(Me)−NH−C(Me)Br2]Br

Abstract

A mixture of solid products was obtained upon absorption of dry HBr by MeCN. One of the products, IH2N=C(Me)--NH--C(Me)Br2IBr, was isolated as white single crystals and characterized by X-ray diffraction analysis.Key words: acetonitrile, hydrogen bromide, X-ray diffraction analysis.It is well known that in many cases hydrogen halides act as specific catalysts of reactions of nitriles. For example, the Pinner reaction (preparation of salts of imino esters), the Hoesch reaction (preparation of salts of ketimines), the Gattermann and Stephen reactions (preparation of salts of aldimines), and a number of other reactions of nitriles are performed with the participation of hydrogen halides and do not proceed when alternative protic or aprotic acids are used. I Therefore, from the first work 2 and on, the direct reactions of nitriles with hydrogen halides attracted the continuing interest of chemists involved in studies of problems of catalysis, t-4Previously, it was believed that complexes containing only one molecule of hydrogen halide are formed upon dissolution of hydrogen halides in nitriles, z However, subsequent studies (primarily, studies of fusibility curves of binary, systems) demonstrated that a number of compounds of different stoichiometric compositions can exist: RCN 9 HX (1) 5, RCN 9 2HX (2) 5,6, 2RCN-HX (3) 7, 2RCN'2HX (4) 7 , 2RCN.3HX (5) 3,5'7 , RCN-5HX (6) 5 , and RCN" 7HX (7) 5 (R = Me, X = C1 or Br). The melting points of most of them are below room temperature. Hydrochloride derivatives have received the most study by IH NMR and [R spectroscopy. Products of hydrolysis and alcoholysis of these derivatives were isolated and characterized, t,7,8Two schemes of interactions of nitriles with hydrogen halides were reported in the literature, t The first scheme, which was suggested based on the UV spectra and on the analysis of the data on the conductivity, assumes that the nitrilium cation [RC=NH] + and the polymeric anion X(HX)-n are formed in solutions. 9 According to the second scheme ([R spectral studies), the solutions contain the imonium halide cation and the halide anion solvated by molecules of hydrogen halide. 3The structural studies of single crystals of composition 2 (X = CI (neutron diffraction study) s or Br (X-ray In this work, we report the results of the structural study of the compound 2RCN-3HX (5a, R = Me and X = Br), which was formed in the reaction mixture of MeCN and HBr. This mixture is used for studying the catalytic reaction of carbonylation of acetylene in the presence of palladium complexes.ll ExperimentalHydrogen bromide was prepared by bromination of anthracene according to a procedure reported previously, tz Reagent-grade bromine and anthracene were used without additional purification. To purify hydrogen bromide from traces of Br 2, it was passed through a U-tube filled with anthracene at a rate of -1.7 mol L-lh -I and then through a Drechsel bottle, which contained MeCN (chemically pure, 11.5 mL) and was cooled with ice (-0 ~ When HBr contacted with MeCN, a finely dispersed ...