An enamine/HB(C6F5)2 adduct as a dormant state in frustrated lewis pair chemistry

Bao Hua Xu; Kathrin Bussmann; Roland Fröhlich; Constantin G. Daniliuc; Jan Gerit Brandenburg; Stefan Grimme; Gerald Kehr; Gerhard Erker

doi:10.1021/om4004225

An enamine/HB(C₆F₅)₂ adduct as a dormant state in frustrated lewis pair chemistry

Bao Hua Xu, Kathrin Bussmann, Roland Fröhlich, Constantin G. Daniliuc, Jan Gerit Brandenburg, Stefan Grimme, Gerald Kehr, Gerhard Erker^*

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

19 Citations (Scopus)

Abstract

The enamine piperidinocyclopentene reacts with HB(C₆F ₅)₂ by formation of the C-Lewis base/B-Lewis acid adduct 10. It shows a zwitterionic iminium ion/hydridoborate structure. However, this adduct formation is apparently reversible and may generate the "invisible" frustrated Lewis pair 11 as a reactive intermediate by hydroboration of the enamine C=C bond in an equilibrium situation at room temperature. Consequently, the FLP 11 was trapped by typical FLP reactions, namely by the reaction with dihydrogen to give the ammonium/hydridoborate 12, the acetylene deprotonation products 13 and 14, and simple borane adducts with pyridine (15) and with an isonitrile (17). The products 10 and 12-15 and the isonitrile adduct 17 were characterized by X-ray diffraction. A DFT study determined the thermodynamic features of the 10 a↔ 11 equilibrium and of a previously discussed reference system (18 a↔ 19) derived by reacting piperidinocyclohexene with HB(C₆F₅)₂.

Original language	English
Pages (from-to)	6745-6752
Number of pages	8
Journal	Organometallics
Volume	32
Issue number	22
DOIs	https://doi.org/10.1021/om4004225
Publication status	Published - 25 Nov 2013
Externally published	Yes

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abstract = "The enamine piperidinocyclopentene reacts with HB(C6F 5)2 by formation of the C-Lewis base/B-Lewis acid adduct 10. It shows a zwitterionic iminium ion/hydridoborate structure. However, this adduct formation is apparently reversible and may generate the {"}invisible{"} frustrated Lewis pair 11 as a reactive intermediate by hydroboration of the enamine C=C bond in an equilibrium situation at room temperature. Consequently, the FLP 11 was trapped by typical FLP reactions, namely by the reaction with dihydrogen to give the ammonium/hydridoborate 12, the acetylene deprotonation products 13 and 14, and simple borane adducts with pyridine (15) and with an isonitrile (17). The products 10 and 12-15 and the isonitrile adduct 17 were characterized by X-ray diffraction. A DFT study determined the thermodynamic features of the 10 a↔ 11 equilibrium and of a previously discussed reference system (18 a↔ 19) derived by reacting piperidinocyclohexene with HB(C6F5)2.",

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T1 - An enamine/HB(C6F5)2 adduct as a dormant state in frustrated lewis pair chemistry

AU - Xu, Bao Hua

AU - Bussmann, Kathrin

AU - Fröhlich, Roland

AU - Daniliuc, Constantin G.

AU - Brandenburg, Jan Gerit

AU - Grimme, Stefan

AU - Kehr, Gerald

AU - Erker, Gerhard

PY - 2013/11/25

Y1 - 2013/11/25

N2 - The enamine piperidinocyclopentene reacts with HB(C6F 5)2 by formation of the C-Lewis base/B-Lewis acid adduct 10. It shows a zwitterionic iminium ion/hydridoborate structure. However, this adduct formation is apparently reversible and may generate the "invisible" frustrated Lewis pair 11 as a reactive intermediate by hydroboration of the enamine C=C bond in an equilibrium situation at room temperature. Consequently, the FLP 11 was trapped by typical FLP reactions, namely by the reaction with dihydrogen to give the ammonium/hydridoborate 12, the acetylene deprotonation products 13 and 14, and simple borane adducts with pyridine (15) and with an isonitrile (17). The products 10 and 12-15 and the isonitrile adduct 17 were characterized by X-ray diffraction. A DFT study determined the thermodynamic features of the 10 a↔ 11 equilibrium and of a previously discussed reference system (18 a↔ 19) derived by reacting piperidinocyclohexene with HB(C6F5)2.

AB - The enamine piperidinocyclopentene reacts with HB(C6F 5)2 by formation of the C-Lewis base/B-Lewis acid adduct 10. It shows a zwitterionic iminium ion/hydridoborate structure. However, this adduct formation is apparently reversible and may generate the "invisible" frustrated Lewis pair 11 as a reactive intermediate by hydroboration of the enamine C=C bond in an equilibrium situation at room temperature. Consequently, the FLP 11 was trapped by typical FLP reactions, namely by the reaction with dihydrogen to give the ammonium/hydridoborate 12, the acetylene deprotonation products 13 and 14, and simple borane adducts with pyridine (15) and with an isonitrile (17). The products 10 and 12-15 and the isonitrile adduct 17 were characterized by X-ray diffraction. A DFT study determined the thermodynamic features of the 10 a↔ 11 equilibrium and of a previously discussed reference system (18 a↔ 19) derived by reacting piperidinocyclohexene with HB(C6F5)2.

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ER -

An enamine/HB(C₆F₅)₂ adduct as a dormant state in frustrated lewis pair chemistry

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