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Structures of the Octahedral Persulfuranes H 4 SF 2 , H 2 SF 4 , Me 2 SH 4 and Me 2 SF 4 , and Activation Enthalpies for Their cis / trans Isomerization
Author(s) -
Steudel Yana,
Steudel Ralf
Publication year - 2003
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200300240
Subject(s) - chemistry , isomerization , octahedron , enthalpy , intramolecular force , molecule , ab initio quantum chemistry methods , crystallography , ab initio , stereochemistry , crystal structure , catalysis , thermodynamics , biochemistry , physics , organic chemistry
Eight hypothetical persulfurane molecules of the type X 2 SY 4 (X, Y = H, F, Me) have been studied by ab initio MO calculations at the G3(MP2) level of theory. Depending on the substituents either the cis or the trans isomers of these octahedral molecules are most stable. While H 4 SF 2 is most stable as the cis isomer, the global minimum structures of H 2 SF 4 , Me 2 SH 4 , and Me 2 SF 4 are the trans isomers. The enthalpy differences between the corresponding isomers are in the range 7−53 kJ·mol −1 . The transition states for the intramolecular cis ⇋ trans isomerization have been located in all cases. Starting from the global minimum geometries the activation enthalpies (Δ H # 298 ) for this isomerization are in the range 199−263 kJ·mol −1 , indicating rather rigid structures. Therefore, it should be possible to isolate both isomers at low to moderate temperatures. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)