Structure and Conformation of 4,4,5,5-Tetrafluoro-1,3,2-Dithiazolidine, S-Nh-S-Cf2-Cf2 - a Gas Electron-Diffraction, X-Ray-Diffraction, and Ab-Initio Study

by Boese, Roland; Oberhammer, H.; Pulay, Peter; Waterfeld, A.

The geometric structure and conformation of the saturated five-membered ring 4,4,5,5-tetrafluoro-1,3,2-dithiazolidine, S-NH-S-CF2-CF2, have been determined in the gas and solid phases by electron and X-ray diffraction, respectively. The equilibrium structure and the total energy along the pseudorotational path have been calculated by ab initio methods (HF/4-21G(*) and HF/TZP). In the gas phase, the five-membered ring adopts a near envelope conformation with one sulfur atom bent out of the CCSN plane and with the N-H bond in the axial direction. The ab initio calculations predict this conformation to be the only stable structure along the pseudorotational path. Two molecules with different conformations are present in the crystal. Whereas one molecule adopts an envelope conformation which is very similar to the gas-phase structure, the other molecule possesses an envelope conformation with the nitrogen atom bent out of the SCCS plane. According to the ab initio calculations, the latter conformation corresponds to a distorted structure and is 1 kcal/mol higher in energy. The two molecules are linked by a nearly linear N...H-N hydrogen bond with N...H = 2.30 angstrom and N...N = 3.099 angstrom.

Journal
Journal of Physical Chemistry
Volume
97
Issue
38
Year
1993
Start Page
9625
ISBN/ISSN
1520-5215; 0022-3654
DOI
10.1021/j100140a017