Formation of N,N,N',N'-Tetramethylformamidinium Disulphide from the Chemical and Electrochemical Oxidation of Tetramethylthiourea. Vibrational Spectra and Crystal Structure of the Chloride Dihydrate Salt.

AGUSTIN EDUARDO BOLZAN, JORGE A. GUIDA, ROBERTO C. V. PIATTI, ALEJANDRO J. ARVIA, OSCAR E. PIRO, J. R. SABINO, EDUARDO E. CASTELLANO

JOURNAL OF MOLECULAR STRUCTURE

Elsevier

Lugar: Amsterdam; Año: 2006

0022-2860

The N,N,N¡¯,N¡¯-tetramethylformamidinium disulphide (TMFDS) was prepared from either the electro-oxidation of tetramethylthiourea (TMTU) on platinum electrodes in aqueous perchloric acid solution or the chemical oxidation of TMTU with hydrogen peroxide in hydrochloric acid-containing absolute ethanol. The electrochemical formation of TMFDS at different potentials was followed by in situ FTIRRAS spectroscopy. The IR and Raman spectra of TMFDS chemically formed as a chloride dihydrate were determined and compared to the product produced electrochemically. The crystal structure of the chloride salt [N(CH3)2]2C=S-S=C [N(CH3)2]2Cl2.2H2O, as determined by X-ray diffractometry, crystallises in the monoclinic C2/c space group with a = 23.267(1), b = 10.824(1), c = 17.774(1) ¢ªA, ¥â = 126.91(1)◦, and Z = 8. The structure was solved from 2489 reflections with I > 2¥ò(I) and refined to an agreement R1-factor of 0.0405. The two molecular halves of the dimericin situ FTIRRAS spectroscopy. The IR and Raman spectra of TMFDS chemically formed as a chloride dihydrate were determined and compared to the product produced electrochemically. The crystal structure of the chloride salt [N(CH3)2]2C=S-S=C [N(CH3)2]2Cl2.2H2O, as determined by X-ray diffractometry, crystallises in the monoclinic C2/c space group with a = 23.267(1), b = 10.824(1), c = 17.774(1) ¢ªA, ¥â = 126.91(1)◦, and Z = 8. The structure was solved from 2489 reflections with I > 2¥ò(I) and refined to an agreement R1-factor of 0.0405. The two molecular halves of the dimeric3)2]2C=S-S=C [N(CH3)2]2Cl2.2H2O, as determined by X-ray diffractometry, crystallises in the monoclinic C2/c space group with a = 23.267(1), b = 10.824(1), c = 17.774(1) ¢ªA, ¥â = 126.91(1)◦, and Z = 8. The structure was solved from 2489 reflections with I > 2¥ò(I) and refined to an agreement R1-factor of 0.0405. The two molecular halves of the dimericC2/c space group with a = 23.267(1), b = 10.824(1), c = 17.774(1) ¢ªA, ¥â = 126.91(1)◦, and Z = 8. The structure was solved from 2489 reflections with I > 2¥ò(I) and refined to an agreement R1-factor of 0.0405. The two molecular halves of the dimeric¥â = 126.91(1)◦, and Z = 8. The structure was solved from 2489 reflections with I > 2¥ò(I) and refined to an agreement R1-factor of 0.0405. The two molecular halves of the dimeric> 2¥ò(I) and refined to an agreement R1-factor of 0.0405. The two molecular halves of the dimeric [N(CH3)2]2C=S-S=C[N(CH3)2]2+2 ion are linked by a disulphide single bond [d(SS)= 2.0454(9) ¢ªA] and related to each other by a non-crystallographic pseudo two-fold axis. DFT structure optimisation and normal mode frequencies were calculated using the 6-311G(d,f) basis set at DFT theory level. An estimation of the free energy for the dimer formation and rate ratio for the homogeneous and heterogeneous processes are presented. These data are consistent with the electrochemical mechanism of the anodic formation of TMFDS2+ from TMTU electro-oxidation in acid solutions. 2.0454(9) ¢ªA] and related to each other by a non-crystallographic pseudo two-fold axis. DFT structure optimisation and normal mode frequencies were calculated using the 6-311G(d,f) basis set at DFT theory level. An estimation of the free energy for the dimer formation and rate ratio for the homogeneous and heterogeneous processes are presented. These data are consistent with the electrochemical mechanism of the anodic formation of TMFDS2+ from TMTU electro-oxidation in acid solutions. solutions.