S S and S P chalcogen bonding in solution: a cryospectroscopic study of the complexes of 2,2,4,4-tetrafluoro-1,3-dithietane with dimethyl sulfide and trimethylphosphineElectronic supplementary information (ESI) available. See DOI: 10.1039/c8nj01648h

In this combined experimental and computational study the complexes formed between 2,2,4,4-tetrafluoro-1,3-dithiethane (C 2 F 4 S 2 ) and the Lewis bases dimethyl sulfide (DMS) and trimethylphosphine (TMP) are studied using infrared spectroscopy of solutions in liquid krypton. For C 2 F 4 S 2 and DMS , ab initio calculations yield two stable chalcogen bonded complex isomers, whereas for C 2 F 4 S 2 and TMP a single chalcogen bonded complex is predicted. In the infrared spectra of solutions containing C 2 F 4 S 2 and DMS, evidence for the presence of two complex bands suggesting the simultaneous occurrence of both calculated complex geometries and the lack of rapid interconversion between them is found for several vibrational modes. The average experimental complexation enthalpy for the 1 : 1 complexes derived from the van't Hoff isochores is −12.3(4) kJ mol −1 . The calculated values obtained by combining a complete basis set extrapolation approach and corrections for zero-point vibrational, thermal and solvent influences are −17.3 and −15.8 kJ mol −1 for the first and second geometry, respectively. For the mixtures of C 2 F 4 S 2 with TMP, single complex bands are found for all vibrational modes, with shifts corresponding well to those calculated for the chalcogen bonded complex. The experimental complexation enthalpy for the C 2 F 4 S 2 ·TMP complex is −13.0(4) kJ mol −1 , whereas the calculated value equals −16.1 kJ mol −1 . Experimental evidence on the formation of S S and P S chalcogen bonded complexes between 2,2,4,4-tetrafluoro-1,3-dithiethane and the Lewis bases dimethyl sulfide and trimethylphosphine is obtained using infrared spectroscopy of solutions in liquid krypton.