Structures and Thermodynamics of the Sulfuranes SF3CN and SF2(CN)2 as well as of the Persulfurane SF4(CN)2 − An ab initio MO Study by the G3(MP2) Method

✍ Scribed by Yana Steudel; Ralf Steudel

• Publisher: John Wiley and Sons
• Year: 2003
• Tongue: English
• Weight: 109 KB
• Volume: 2003
• Category: Article
• ISSN: 1434-1948
• DOI: 10.1002/ejic.200300027

✦ Synopsis

Abstract

At the G3(MP2) level of theory the trans isomer 1a of the hypothetical molecule SF~4~(CN)~2~ is more stable than the cis isomer 1b by 8 kJ·mol^−1^. The isomerization of 1a to 1b requires an activation enthalpy of 319 kJ·mol^−1^ at 298 K. The decomposition of trans‐SF~4~(CN)~2~ to SF~2~(CN)~2~ and F~2~ is endothermic (Δ__H__^o^~298~ = 395 kJ·mol^−1^) but the elimination of FCN from trans‐SF~4~(CN)~2~ is exothermic by −7 kJ·mol^−1^. The elimination of (CN)~2~ from cis‐SF~4~(CN)~2~ is exothermic by −137 kJ·mol^−1^. The activation enthalpies for the latter two reactions were calculated as 251 and 311 kJ·mol^−1^, respectively. Thus, SF~4~(CN)~2~ should be a thermally stable compound. In the sulfuranes SF~3~CN and SF~2~(CN)~2~ the CN ligands prefer the equatorial positions; mutual exchange of an axial F atom by an equatorial CN group requires a reaction enthalpy of 51 kJ·mol^−1^ [SF~3~CN] or 58 kJ·mol^−1^ [SF~2~(CN)~2~]. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)