Dihydrogen Bond in the Aminoborane Complex of a Nicergoline Intermediate

• Main Authors: Jan Čejka, Ladislav Cvak, Simona Žižková, Bohumil Kratochvíl, Alexandr Jegorov
• Format: Article
• Language: English
• Published: MDPI AG 2019-07-01
• Series: Molecules
• Subjects: nicergoline; aminoborane; CSD; single crystal; X-ray structure; dihydrogen bond
• Online Access: https://www.mdpi.com/1420-3049/24/14/2548

An aminoborane side product from the nicergoline manufacture process was identified by single-crystal X-ray diffraction. As boranes of pharmaceutical molecules are quite rare, the binding potential of the BH₃ group was investigated and compared with similar compounds using Cambridge Structural Database (CSD). Surprisingly, the packing was stabilized by a dihydrogen bond, which triggered a false alert for too-short contact of hydrogen atoms in IUCR checkCIF. As the dihydrogen bond concept is not widely known, such an alert might mislead crystallographers to force −CH₃ optimal geometry to −BH₃ groups. The B−H distances equal to or less than 1.0 Å (17% of the CSD structures) are substantially biased when analyzing the structures of aminoborane complexes in CSD. To conduct proper searching, B−H bond length normalization should be applied in the CSD search.