Frustrated Lewis Pair Chemistry Derived from Bulky Allenyl and Propargyl Phosphanes |
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| Authors: | Dr Christoph Rosorius Jennifer Möricke Birgit Wibbeling Dr Alison C McQuilken Prof?Dr Timothy H Warren Dr Constantin G Daniliuc Dr Gerald Kehr Prof?Dr Gerhard Erker |
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| Institution: | 1. Organisch-Chemisches Institut, Universit?t Münster, Münster, Germany;2. Department of Chemistry, Georgetown University, Washington DC, USA |
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| Abstract: | The dimesitylpropargylphosphanes mes2P?CH2?C≡C?R 6 a (R=H), 6 b (R=CH3), 6 c (R=SiMe3) and the allene mes2P?C(CH3)=C=CH2 ( 8 ) were reacted with Piers’ borane, HB(C6F5)2. Compound 6 a gave mes2PCH2CH=CH(B(C6F5)2] ( 9 a ). In contrast, addition of HB(C6F5)2 to 6 b and 6 c gave mixtures of 9 b (R=CH3) and 9 c (R=SiMe3) with the regioisomers mes2P?CH2?CB(C6F5)2]=CRH 2 b (R=CH3) and 2 c (R=SiMe3), respectively. Compounds 2 b , c underwent rapid phosphane/borane (P/B) frustrated Lewis pair (FLP) reactions under mild conditions. Compound 2 c reacted with nitric oxide (NO) to give the persistent FLP NO radical 11 . The systems 2 b , c cleaved dihydrogen at room temperature to give the respective phosphonium/hydridoborate products 13 b , c . Compound 13 c transferred the H+/H? pair to a small series of enamines. Compound 13 c was also a metal‐free catalyst (5 mol %) for the hydrogenation of the enamines. The allene 8 reacted with B(C6F5)3 to give the zwitterionic phosphonium/borate 17 . The ‐PPh2‐substituted mes2P‐propargyl system 6 d underwent a typical 1,2‐P/B‐addition reaction to the C≡C triple bond to form the phosphetium/borate zwitterion 20 . Several products were characterized by X‐ray diffraction. |
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| Keywords: | boranes hydroboration hydrogen activation phosphanes X-ray diffraction |
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