Premium
Charge‐Transfer Complexes between the Sulfur Molecules SO 2 , S 2 O, S 3 , SONH, and SOCl 2 and the Amine Donors NH 3 and NMe 3 – A Theoretical Study
Author(s) -
Steudel Ralf,
Steudel Yana
Publication year - 2007
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.200700399
Subject(s) - chemistry , adduct , molecule , acceptor , amine gas treating , sulfur , enthalpy , chemical polarity , crystallography , organic chemistry , thermodynamics , condensed matter physics , physics
The formation of adducts between the acceptor molecules SO 2 , S 2 O, S 3 , and SOCl 2 and the donor molecules ammonia and trimethylamine has been studied by high‐level G3X(MP2) theory, in most cases for the first time. Minimum energy structures with a 1:1 composition and with sulfur–nitrogen bonds have been located for all complexes. The thermodynamic properties, vibrational spectra, and atomic charges of these molecules have been calculated. Of the 10 investigated complexes, only SO 2 · NMe 3 ( 2 ) and S 2 O · NMe 3 ( 4 ) are predicted to be thermodynamically stable in the gas phase under standard conditions (Δ G ° 298 < 0). However, all adducts except S 3 · NH 3 ( 5 ), SOCl 2 · NH 3 ( 7 ), and SOCl 2 · NMe 3 ( 8 ) are stable thermodynamically at 77 K. In a polar continuum with a dielectric constant ( ϵ ) of 40, complexes 2 , 4 , and S 3 · NMe 3 ( 6 ) are stable even at 25 °C. However, if the adducts are formed in the polar continuum from the gaseous components, all adducts except S 3 · NH 3 are formed not only exothermally but also exergonically. Complexes 2 , 4 , and 8 are the only species known in the solid state so far. The charge transfer from donor to acceptor in the various complexes in the gas phase ranges from 0.08 to 0.39 electrostatic units and correlates inversely with the S–N bond length, which ranges from 198 to 295 pm. In general, the charge transfer weakens the bonds within the acceptor molecule, which therefore may be considered to become activated. The formation of thionyl imide (SONH) from SOCl 2 and NH 3 is exergonic in the gas phase and the interaction between SONH and NH 3 is very weak. In the case of SO 2 , the 1:2 complexes SO 2 · 2NH 3 ( 1a ) and SO 2 · 2NMe 3 ( 2a ), which contain two S–N bonds, are unstable with respect to their three‐component molecules both in the gas phase and in a polar medium at 25 °C, but they are stable in the polar phase with respect to the gaseous components.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)