ИСТИНА

Salt solutions Cu(OTf)2 and Fe(OTf)3 in DEA (OTf – triflate anion CF3SO3–, DEA – diethanolamine HN(CH2CH2OH)2) were named “ionic liquids” in papers [1-2] and their indicated structure [M(DEA)6](OTf)n corresponded to coordination compounds. Later the same group of authors has established [3] the structure of crystals, isolated from the mixture Cu(OTf)2+DEA. Composition and structure of the complex compound were very different from previously proposed for ionic liquid containing copper, namely: [Cu(DEA)(DEA-H)]OTf, where DEA-H is DEA molecule with a deprotonated alcohol group. Both ligands DEA are chelate one. Systems Cu(OTf)2+6DEA and Fe(OTf)3+6DEA were studied [4] by methods EXAFS и DTA-МS. We have shown that CN of copper atom in solution does not exceed 4, but it is equal to 6 in the case of iron atom. In this regard, it was concluded that system Cu(OTf)2+DEA consists of the copper complex [Cu(DEA)(DEA-H)]OTf and solvent DEA4HOTf. System Fe(OTf)3+6DEA is presumably solution of complex compound [Fe(DEA)3] (OTf)3 with chelate ligands DEA in excess of DEA. In order to study the solvent DEA4HOTf we investigated mixtures with molar ratios DEA/HOTf and DEA/HNO3 = 9/1, 4/1, 3/1, 3/2, 1/1, 1/2, 1/3 and pure DEA by methods 1H-NMR and DSC. It was found out that the chemical shift value of the combined (due to fast exchange of protons) signal of amine and alcohol groups in 1H-NMR spectra grows when the composition changes from pure DEA to the ratio DEA/HOTf and DEA/HNO3 = 4/1and after that point remains constant, what may indicate the existence of a compound of formula DEA4HOTf, which decomposes at elevated temperatures without DEA evaporation while DEA is volatile in the system Fe(OTf)3+6DEA. The difference between systems DEA+HOTf and DEA+HNO3 consists only in the fact that with the ratio DEA/acid=1/1 signals of amine and alcohol groups exist separately (rapid exchange of protons is interrupted) in the former system but the combined signal is stored in the later. To find out the reasons for the differences a salt DEA.HNO3 was studied by X-ray crystal structure analysis and 1H-MAS NMR. In connection with the discovery of a concert mechanism for the exchange of protons in alcohols [5, 6] the role of protons in the systems under study is discussed as unique complexing agents. [1] T. M. Anderson, D. Ingersoll, A. J. Rose, C. L. Staiger and J. C. Leonard, Dalton Trans., 2010, 39, 8609–8612. [2] H. D. Pratt III, A. J. Rose, C. L. Staiger, D. Ingersoll and T. M. Anderson, Dalton Trans., 2011, 40, 11396–11401. [3] H. D. Pratt III, J. C. Leonard, L. A. M. Steele, C. L. Staiger, T. M. Anderson, Inorg. Chim. Acta, 2013, 396, 78–83 [4] M. A. Zakharov, G. V. Fetisov, A. A. Veligzhanin, M. A. Bykov, K. A. Paseshnichenko, S. F. Dunaev and L. A. Aslanov, Dalton Trans., 2015, 44, 18576–18584. [5] E. S. Stoyanov, I. V. Stoyanova, and C. A. Reed, Chem. Eur. J. , 2008, 14, 3596 – 3604. [6] N. Solca, and O. Dopfer, J. Phys. Chem. A, 2005, 109, 6174-6186. Acknowledgements – This study was supported by Lomonosov Moscow State University Program of Development. e-mail: aslanov@struct.chem.msu.ru