INFRARED MATRIX-ISOLATION STUDIES OF HYDROGEN-BONDS INVOLVING C-H BONDS - ALKENES WITH SELECTED BASES

Hydrogen-bonded complexes of ethene and substituted ethenes with strong bases have been isolated and characterized for the first time in argon matrices at 15 K. Coordination of the alkenic hydrogen to the electron donor was evidenced by distinct red shifts of the C-H stretching mode in the infrared spectrum. These shifts ranged from 10 to 150 cm-1 and are considerably less than those observed previously for the corresponding alkynic complexes, suggesting a distinct but quite weak interaction. The perturbed ethenic hydrogen bending modes and carbon- halogen stretching modes were also observed for a number of systems. The larger the number of halogens on the substituted ethene, the larger the shifts, while fluorinated ethenes gave rise to larger shifts than their chlorine counterparts. Finally, trans-1,2-dichloroethene consistently gave rise to larger shifts with a given base than did the corresponding cis compound. © 1990 American Chemical Society.