Thermal and catalytic dehydrogenation of the guanidine-borane adducts H3B hppH (hppH = 1,3,4,6,7,8-hexahydro-2H-pyrimido(1,2-a)pyrimidine) and H3B N(H)C(NMe2)2

• Verfasst von: Ciobanu, Oxana [VerfasserIn]
• Verfasst von: Allouti, Fayçal [VerfasserIn]
• Verfasst von: Roquette, Pascal [VerfasserIn]
• Verfasst von: Leingang, Simone [VerfasserIn]
• Verfasst von: Enders, Markus [VerfasserIn]
• Verfasst von: Wadepohl, Hubert [VerfasserIn]
• Verfasst von: Himmel, Hans-Jörg [VerfasserIn]
• Titel: Thermal and catalytic dehydrogenation of the guanidine-borane adducts H3B hppH (hppH = 1,3,4,6,7,8-hexahydro-2H-pyrimido(1,2-a)pyrimidine) and H3B N(H)C(NMe2)2
• Titelzusatz: a combined experimental and quantum chemical study
• Verf.angabe: Oxana Ciobanu, Fayçal Allouti, Pascal Roquette, Simone Leingang, Markus Enders, Hubert Wadepohl, and Hans-Jörg Himmel
• Jahr: 2008
• Umfang: 12 S.
• Fussnoten: Die Buchstaben "H" und "a" im Ausdruck "2H-pyrimido[1,2-a]" sind kursiv dargestellt ; Im Titel ist die Zahl "3" im Ausdruck "H3B hppH" und "H3B N(H)C(NMe2)2" sowie die Zahl "2" im Ausdruck "H3B N(H)C(NMe2)2"tiefgestellt ; First published: 28 November 2008 ; Gesehen am 01.12.2022
• Titel Quelle: Enthalten in: European journal of inorganic chemistry
• Ort Quelle: Weinheim : Wiley-VCH, 1998
• Jahr Quelle: 2008
• Band/Heft Quelle: (2008), 35, Seite 5482-5493
• ISSN Quelle: 1099-0682
• DOI: doi:10.1002/ejic.200800564
• Datenträger: Online-Ressource
• Sprache: eng
• Sach-SW: Boron
• Sach-SW: Dehydrogenation
• Sach-SW: Density functional calculations
• Sach-SW: Heterogeneous catalysis
• Sach-SW: Homogeneous catalysis
• Sach-SW: Hydrogen
• K10plus-PPN: 1824124945

Abstract

Herein thermal and catalytic dehydrogenation of the guanidine-borane adducts H3B·hppH (hppH = 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine) and H3B·N(H)C(NMe2)2 are analysed. Thermal decomposition of H3B·hppH at 80 °C leads to [HB(μ-hpp)]2 and a second boron hydride, which is tentatively identified as [(κ2N-hpp)BH2]. Decomposition in boiling toluene (110 °C) leads to a mixture of [H2B(μ-hpp)]2 and [HB(μ-hpp)]2, from which [H2B(μ-hpp)]2 can be separated and crystallised. In the presence of a catalyst (with Cp2TiCl2/nBuLi or [Rh(1,5-cod)Cl]2 as precatalysts) dehydrogenation at 80 °C leads predominantly to [H2B(μ-hpp)]2. In the case of H3B·N(H)C(NMe2)2 uncatalysed dehydrogenation turns out to be a very slow process even at 110 °C. Interestingly, the ultimate product of this process is oligomeric methylimino borane, [HBNMe]n. This pathway can be modelled and understood with the aid of quantum chemical calculations. Faster dehydrogenation can be initiated by addition of a catalyst. Finally, the possible mechanisms for thermal and Cp2Ti-catalysed dehydrogenation are analysed for the model compound H3B·N(H)C(NH2)2 by means of quantum chemical (DFT) calculations.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)