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Paper | Special issue | Vol 79, No. 1, 2009, pp.531-548
Published online, 22nd September, 2008
DOI: 10.3987/COM-08-S(D)13
Synthesis, Structure and Catalytic Activity of Macrocyclic NHC Pd Pincer Complexes

Noriaki Watarai, Hiroyasu Kawasaki, Isao Azumaya, Ryu Yamasaki, and Shinichi Saito*

*Department of Chemistry, Faculty of Science, Tokyo University of Science, Kagurazaka, Shinjuku, Tokyo 162-8601, Japan

Abstract

We synthesized a series of new N-heterocyclic carbene (NHC) macrocyclic Pd pincer complexes (17-22) by the reaction of Pd(OAc)2 or Pd2(dba)3 with the corresponding macrocycles, which were prepared by the coupling reaction of dibromides with bisimidazoles. The complex adopted twisted conformation, and the activation energy of the conformational interconversion of the macrocycle was determined by VT-NMR. We also examined the catalytic activity of these Pd complexes in Mizoroki-Heck and oxidative alkynyl-alkynyl homocoupling reactions.