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Hindered Rotation in New Air-Stable Ruthenium Olefin Metathesis Catalysts with Chromanylmethylidene Ligands
Agnieszka
Hryniewicka A,
Jacek W.
Morzycki A D,
Leszek
Siergiejczyk A,
Stanisław
Witkowski A D,
Jacek
Wójcik B,
Adam
Gryff-Keller C
A
Institute of Chemistry, University of Białystok, al. Piłsudskiego 11/4, 15-443 Białystok, Poland.
B
Institute of Biochemistry and Biophysics, Polish Academy of Sciences, ul. Pawińskiego 5a, 02-106 Warsaw, Poland; Institute of Organic Chemistry, Polish Academy of Sciences, ul. Kasprzaka 44/52, 01-244 Warsaw, Poland.
C
Faculty of Chemistry, Warsaw University of Technology, ul. Noakowskiego 3, 00-664 Warsaw, Poland.
D
Corresponding authors. Email: morzycki@uwb.edu.pl; wit@uwb.edu.pl
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Australian Journal of Chemistry 62(10) 1363–1370 http://dx.doi.org/10.1071/CH08443
Submitted: 18 October 2008
Accepted: 26 January 2009
Published online: 13 October 2009
Abstract
Three new ruthenium complexes with chromanylmethylidene ligands were synthesized and dynamic NMR analysis of these compounds was carried out. The activation energy for the C–Ru rotation was measured for the first time and found to be of ~60 kJ mol–1. The complexes may potentially serve as latent catalysts for olefin metathesis – they promote the simple ring-closing metathesis reactions very slowly at room temperature, but are much more active at slightly elevated temperatures. No asymmetric induction was observed when the chiral α-tocopherol-derived catalyst was used.
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