Evidence of Dihydrogen Bonding of a Chiral Amine–Borane Complex in Solution by VCD Spectroscopy†
This research was supported by the University of Alberta, the Natural Sciences and Engineering Research Council of Canada, and the Cluster of Excellence RESOLV (EXC 1069) of the Deutsche Forschungsgemeinschaft (DFG). We thank Prof. Eric Rivard for access to the synthesis equipment. C.M. acknowledges financial support by the Fonds der chemischen Industrie for a Liebig fellowship. Y.X. holds a Tier I (senior) Canada Research Chair in Chirality and Chirality Recognition. VCD=vibrational circular dichroism.
Graphical Abstract
A chiral amine–borane is investigated by vibrational circular dichroism (VCD) spectroscopy. By comparison of experimental and calculated spectra, a unique VCD pattern associated with the formation of dihydrogen-bonded dimers in solution is identified. Different dihydrogen binding arrangements in solution and in the solid state are characterized.
Abstract
IR and vibrational circular dichroism (VCD) spectra of a chiral amine–borane in solution are investigated. By comparison of experimental and calculated spectra, unique VCD spectral signatures, which can be attributed to the formation of dihydrogen-bonded dimers in solution, are identified for the first time. These VCD features are highly sensitive to the specific dihydrogen-bonding topologies utilized by the chiral amine–borane subunits and thus provide direct structural information of these dihydrogen-bonded species in solution. Differences in the dihydrogen binding arrangements in solution and in solid state are also revealed.
