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Intermolecular Interactions of a Chiral Amine Borane Adduct Revealed by VCD Spectroscopy

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journal contribution
posted on 02.06.2016, 00:00 by Tobias Osowski, Julia Golbek, Klaus Merz, Christian Merten
Amine boranes feature strong hydrogen bonding acceptor and donor moieties in close proximity, leading, for instance, to dihydrogen bonding driven self-aggregation. In this work, the infrared (IR) and vibrational circular dichroism (VCD) spectra of the bulky bis­(α-phenylethyl)­amine borane 1 in chloroform and acetonitrile solution are reported. By comparison with calculated spectra, the VCD spectral features observed in chloroform solution can clearly be associated with the presence of monomeric species. A shift of the conformational preferences occurs when changing the solvent to acetonitrile, which can only be deduced from the VCD spectral signatures but not from the IR spectrum. Using variable-temperature IR and VCD spectroscopy, the dihydrogen bonded dimeric species is characterized experimentally at −50 °C and theoretically by means of density functional theory calculations.