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Taking the halogen bonding–hydrogen bonding competition one step further: complexes of difluoroiodomethane with trimethylphosphine, dimethyl sulfide and chloromethane
Author(s) -
Geboes Yannick,
De Proft Frank,
Herrebout Wouter A.
Publication year - 2017
Publication title -
acta crystallographica section b
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.604
H-Index - 33
ISSN - 2052-5206
DOI - 10.1107/s2052520617001354
Subject(s) - chloromethane , trimethylphosphine , dimethyl sulfide , halogen , chemistry , hydrogen bond , competition (biology) , halogen bond , hydrogen sulfide , sulfide , crystallography , catalysis , organic chemistry , crystal structure , molecule , sulfur , alkyl , ecology , biology
To rationalize the driving factors in the competition of halogen bonding and hydrogen bonding, the complexes of the combined halogen‐/hydrogen‐bond donor difluoroiodomethane with the Lewis bases trimethylphosphine, dimethyl sulfide and chloromethane are studied. For all Lewis bases, ab initio calculations lead to halogen‐ and hydrogen‐bonded complexes. Fourier transform–IR experiments involving solutions of mixtures of difluoroiodomethane with trimethylphosphine(‐ d 9 ) or dimethyl sulfide(‐ d 6 ) in liquid krypton confirm the coexistence of a halogen‐bonded and hydrogen‐bonded complex. Also for solutions containing chloromethane, evidence of the formation of binary associations is found, but no definitive assignment of the multiple complex bands could be made. Using van't Hoff plots, the experimental complexation enthalpies for the halogen‐ and hydrogen‐bonded complex of difluoroiodomethane with trimethylphosphine are determined to be −15.4 (4) and −10.5 (3) kJ mol −1 , respectively, while for the halogen‐ and hydrogen‐bonded complexes with dimethyl sulfide, the values are −11.3 (5) and −7.7 (6) kJ mol −1 , respectively. The experimental observation that for both trimethylphospine and dimethyl sulfide the halogen‐bonded complex is more stable than the hydrogen‐bonded complex supports the finding that softer Lewis bases tend to favor iodine halogen bonding over hydrogen bonding.