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Exploring the Limits of Frustrated Lewis Pair Chemistry with Alkynes: Detection of a System that Favors 1,1‐Carboboration over Cooperative 1,2‐P/B‐Addition
Author(s) -
Chen Chao,
Eweiner Florian,
Wibbeling Birgit,
Fröhlich Roland,
Senda Shunsuke,
Ohki Yasuhiro,
Tatsumi Kazuyuki,
Grimme Stefan,
Kehr Gerald,
Erker Gerhard
Publication year - 2010
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.201000189
Subject(s) - borane , frustrated lewis pair , hydroboration , chemistry , lewis acids and bases , deprotonation , metallocene , boranes , medicinal chemistry , stereochemistry , triple bond , organometallic chemistry , polymer chemistry , double bond , boron , organic chemistry , catalysis , polymerization , ion , polymer
The zirconocene complex [{(C 6 F 5 ) 2 B‐(CH 2 ) 3 ‐Cp}(Cp‐P t Bu 2 )ZrCl 2 ] ( 6 ; Cp=cyclo‐C 5 H 4 ) was prepared by hydroboration of [(allyl‐Cp)(Cp‐P t Bu 2 )ZrCl 2 ] ( 5 ) with HB(C 6 F 5 ) 2 (“Piers’ borane”). It represents a frustrated Lewis pair (FLP) in which both the Lewis acid and the Lewis base were attached at the metallocene framework. Its reaction with 1‐pentyne did not result in the 1,2‐addition of or deprotonation reaction by the FLP, but rather in the 1,1‐carboboration of the triple bond, thereby obtaining a Z / E mixture (1.2:1) of the respective organometallic substituted alkenes 7 . The analogous reaction of 1‐pentyne with the phosphorous‐free system [{(C 6 F 5 ) 2 B‐(CH 2 ) 3 ‐Cp)}CpZrCl 2 ] ( 9 ) gave the respective 1,1‐carboboration products ( Z‐10 / E‐10 ≈1.3:1).