Porphyrins fused to N-heterocyclic carbene palladium complexes as tunable precatalysts in Mizoroki-Heck reactions: How the porphyrin can modulate the apparent catalytic activity?
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- 作者：Jean-Franç ; ois Lefebvre ; Jean-Franç ; ois Longevial ; Karine Molvinger ; Sé ; bastien Clé ; ment ; Sé ; bastien Richeter ; sricheter@univ-montp2.fr" class="auth_mail" title="E-mail the corresponding author
- 关键词：Porphyrins ; N-heterocyclic carbenes ; Heck reaction ; Palladium complexes ; Nanoparticles
- 刊名：Comptes Rendus Chimie
- 出版年：2016
- 出版时间：January-February 2016
- 年：2016
- 卷：19
- 期：1-2
- 页码：94-102
- 全文大小：1026 K
文摘
Porphyrins fused to N-heterocyclic carbenes (NHCs) 1M, with inner metal M = Ni, Cu, Zn and H2, were used to synthesize palladium(II) complexes. These complexes behaved as precatalysts for high-temperature Mizoroki–Heck reactions between iodobenzene and styrene. Despite similar electronic properties between 1M ligands, catalytic activity was found to significantly depend on the presence, or not, of a central metal incorporated in the porphyrin core: a conversion of iodobenzene between 80–90% was observed with metalloporphyrins (M = Ni, Cu and Zn), whereas only 30% was observed with free-base porphyrins (M = H2) after 10 h. Palladium leaching and subsequent trapping of free palladium in the inner core of the free-base porphyrin modified the concentration of Pd(0) active species and may explain the lower catalytic activity observed.