Evidence for a rapid degenerate hetero-Cope-type rearrangement in [Cp*W(S)2S-CH2-CH=CH2]

Florian Eweiner; Shunsuke Senda; Klaus Bergander; Christian Mück-Lichtenfeld; Stefan Grimme; Roland Fröhlich; Michiko Aoyama; Hiroyuki Kawaguchi; Yasuhiro Ohki; Tsuyoshi Matsumoto; Gerald Kehr; Kazuyuki Tatsumi; Gerhard Erker

doi:10.1002/asia.200900360

Evidence for a rapid degenerate hetero-Cope-type rearrangement in [Cp*W(S)2S-CH2-CH=CH2]

Chem Asian J. 2009 Dec 1;4(12):1830-1833. doi: 10.1002/asia.200900360.

Affiliations

¹ Organisch-Chemisches Institut, Westfälische Wilhelms Universität Münster, Corrensstraße 40,D-48149 Münster (Germany), Fax: (+49) 251-83-36503.
² Department of Chemistry, Faculty of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602 (Japan).

PMID: 19885900
DOI: 10.1002/asia.200900360

Abstract

Treatment of the salt [PPh(4)]+[Cp*W(S)3]- (6) with allyl bromide gave the neutral complex [Cp*W(S)2S-CH2-CH=CH2] (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 DeltaG(not equal) (278 K) approximately 13.7+/-0.1 kcal mol(-1) was obtained [DeltaH(not equal) approximately 10.4+/-0.1 kcal mol(-1); DeltaS(not equal) approximately -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.