Access to FeII Bis(σ‐B−H) Aminoborane Complexes through Protonation of a Borohydride Complex and Dehydrogenation of Amine‐Boranes

• Published in: Angewandte Chemie International Edition 2019-09, Vol.58 (39), p.13874-13879
• Main Authors: Gorgas, Nikolaus, Stöger, Berthold, Veiros, Luis F., Kirchner, Karl
• Format: Article
• Language: English
• Subjects: (σ-B−H) complexes; aminoboranes; ammonia-borane; Ammonium; Ammonium salts; Boranes; Borohydrides; Coordination compounds; Crystallography; Dehydrogenation; Iron; Magnetic resonance spectroscopy; NMR; NMR spectroscopy; Nuclear magnetic resonance; Protonation; Salts; Structural analysis
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201906971

Herein, we report on the first synthesis and structural characterization of the iron based aminoborane complexes [Fe(PNP)(H)(η2:η2‐H2B=NR2)]+ (R=H, Me). These species are formed upon protonation of the borohydride complex [Fe(PNP)(H)(η2‐BH4)] by ammonium salts [NH2R2]+ (R=H, Me). For R=Me, the reaction proceeds via the cationic dinuclear intermediate [{Fe(PNP)(H)}2(μ2,η2:η2‐BH4)]+. A mechanism for the reaction is proposed based on DFT calculations that also indicate the final aminoborane complex as the thermodynamic product. All complexes were characterized by NMR spectroscopy, HRMS, and X‐ray crystallography. The first synthesis and structural characterization of FeII based aminoborane complexes of the type [Fe(PNP)(H)(η2:η2‐H2B=NR2)]+ (R=H, Me) is reported. These species are formed upon protonation of the borohydride complex [Fe(PNP)(H)(η2‐BH4)] by ammonium salts NH2R2+ (R=H, Me).