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Frustrated Lewis Pair Chemistry Derived from Bulky Allenyl and Propargyl Phosphanes
Author(s) -
Rosorius Christoph,
Möricke Jennifer,
Wibbeling Birgit,
McQuilken Alison C.,
Warren Timothy H.,
Daniliuc Constantin G.,
Kehr Gerald,
Erker Gerhard
Publication year - 2016
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201502493
Subject(s) - allene , borane , chemistry , phosphonium , propargyl , frustrated lewis pair , boron trifluoride , triple bond , medicinal chemistry , lewis acids and bases , zwitterion , stereochemistry , boron , catalysis , double bond , molecule , polymer chemistry , organic chemistry
The dimesitylpropargylphosphanes mes 2 P−CH 2 −C≡C−R 6 a (R=H), 6 b (R=CH 3 ), 6 c (R=SiMe 3 ) and the allene mes 2 P−C(CH 3 )=C=CH 2 ( 8 ) were reacted with Piers’ borane, HB(C 6 F 5 ) 2 . Compound 6 a gave mes 2 PCH 2 CH=CH(B(C 6 F 5 ) 2 ] ( 9 a ). In contrast, addition of HB(C 6 F 5 ) 2 to 6 b and 6 c gave mixtures of 9 b (R=CH 3 ) and 9 c (R=SiMe 3 ) with the regioisomers mes 2 P−CH 2 −C[B(C 6 F 5 ) 2 ]=CRH 2 b (R=CH 3 ) and 2 c (R=SiMe 3 ), 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(C 6 F 5 ) 3 to give the zwitterionic phosphonium/borate 17 . The ‐PPh 2 ‐substituted mes 2 P‐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.