The crystal and molecular structure of 5-amino-2-thiol-l,3,4-thiadiazole

Abstract

The crystal structure of 5-amino-2-thiol-l,3,4-thiadiazole (C2H3NaS2) has been determined by threedimensional Patterson and Fourier methods and refined by block-matrix least-squares calculations.The crystals are monoclinic, space group P21/c with four molecules in a unit cell of dimensions a = 6.167, b= 10.048, c=9-007,~, fl=116.8 °. The final R index is 0.106 for 796 observed reflexions, collected with Cu K0c radiation. The molecule may be regarded as being planar since the deviations of the atoms from the mean plane of the molecule are all less than 0.02/~. Bond lengths indicate that the compound exists in the thione rather than the thiol form. The 1,3,4-thiadiazole ring possesses a fair degree of aromaticity with a localized C(1)=N(1)double bond of length 1.305 (6) ~. Other C-N bond lengths are 1.334 and 1.339 ~ with a mean estimated standard deviation of 0.009 A. The N-N bond length is 1.382 (8) A,. The cyclic C-S distances are 1.746 and 1.748 A and the exocyclic C-S bond length is 1"678 A, the mean e.s.d, of these three bonds is 0.006 ~. Of particular interest is the short S-S intramolecular contact of 3.008 A which is approximately 0.5 A shorter than the sum of the Pauling van der Waals radii. There is a reasonable probability that hydrogen bonds of type N-H. • • S and length 3"32 A exist, joining pairs of molecules across centres of symmetry.

The crystal and molecular structure of 2-mercaptobenzimidazole

“…The C(2)-S(2) length of 1.671 A possesses 80% double-bond character on Abraham's (1956) scale and is typical of exocyclic thiones (Downie, Harrison, Raper & Hepworth, 1972). This confirms the thione nature of the compound in the solid (Fig.…”

An assessment to evaluate the validity of different methods for the description of some corrosion inhibitors

“…A major class of tautomeric reactions involves the exchange of a hydrogen atom between the two other atoms in the same molecule, in both cases forming a covalent bond. The tautomeric interconversion, e.g., keto-enol, imine-enamine, and nitroso-oxime, have been extensively studied [40][41][42] and these studies showed that the tautomerism is important for the stability. The calculations showed that the tautomerism in the case of the MTA compound allows being present in the form of another isomer.…”

trans-Bis(5-amino-1,3,4-thiadiazol-2-thiolato-κS2)bis(triphenylphosphane-κP)palladium(II) dimethyl sulfoxide disolvate hemihydrate

“…For SSNH 2 acting as a ligand and as auxiliary in the construction of hydrogen bonds in coordination compounds with Pd II , see , with Pt II , see: Tannai et al (2006), with Cd II , see: Gao et al (2009) and with Au I , see: Tzeng et al (1999) ;Tzeng, Huang et al (2004). For the thiolate form, see: Downie et al (1972).…”