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Evidence for a Rapid Degenerate Hetero‐Cope‐Type Rearrangement in [Cp*W(S) 2 S‐CH 2 ‐CHCH 2 ]
Author(s) -
Eweiner Florian,
Senda Shunsuke,
Bergander Klaus,
MückLichtenfeld Christian,
Grimme Stefan,
Fröhlich Roland,
Aoyama Michiko,
Kawaguchi Hiroyuki,
Ohki Yasuhiro,
Matsumoto Tsuyoshi,
Kehr Gerald,
Tatsumi Kazuyuki,
Erker Gerhard
Publication year - 2009
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.200900360
Subject(s) - allyl bromide , chemistry , crystallography , nmr spectra database , gibbs free energy , spectral line , transition metal , crystal structure , bromide , stereochemistry , medicinal chemistry , physics , catalysis , inorganic chemistry , thermodynamics , organic chemistry , astronomy
Treatment of the salt [PPh 4 ] + [Cp*W(S) 3 ] − ( 6 ) with allyl bromide gave the neutral complex [Cp*W(S) 2 S‐CH 2 ‐CHCH 2 ] ( 7 ). The product 7 was characterized by an X‐ray crystal structure analysis. Complex 7 features dynamic NMR spectra that indicate a rapid allyl automerization process. From the analysis of the temperature‐dependent NMR spectra a Gibbs activation energy of Δ G ≠ (278 K)≈13.7±0.1 kcal mol −1 was obtained [Δ H ≠ ≈10.4±0.1 kcal mol −1 ; Δ S ≠ ≈−11.4 cal mol −1 K −1 ]. The DFT calculation identified an energetically unfavorable four‐membered transition state of the “forbidden” reaction and a favorable six‐membered transition state of the “Cope‐type” allyl rearrangement process at this transition‐metal complex core.