Issue 38, 2019

Palladium complexes of N-heterocyclic carbenes displaying an unsymmetrical N-alkylfluorenyl/N′-aryl substitution pattern and their behaviour in Suzuki–Miyaura cross coupling

Abstract

A series of new Pd–PEPPSI complexes containing imidazolylidene ligands with a mixed 9-alkyl-9-fluorenyl/aryl N,N′-substitution pattern have been synthesised. Single crystal X-ray diffraction studies were carried out for four complexes, which revealed that the N-heterocyclic carbene ligands display a semi-open, unsymmetrical space occupancy about the metal. Despite their particular unsymmetrical shape, the new complexes were found to perform as well in Suzuki–Miyaura cross coupling (dioxane, 80 °C) as previously reported, highly active analogues bearing two sterically protecting 9-alkylfluorenyl substituents. They were further found to be considerably more active than the standard Pd–PEPPSI complexes [PdCl2IMes(pyridine)] and [PdCl2IPr(pyridine)]. Surprisingly, unlike the latter, the unsymmetrical complexes of this study were practically inactive in isopropanol at 80 °C. Under these conditions the complexes appear to decompose with formation of non-stabilised nanoparticles.

Graphical abstract: Palladium complexes of N-heterocyclic carbenes displaying an unsymmetrical N-alkylfluorenyl/N′-aryl substitution pattern and their behaviour in Suzuki–Miyaura cross coupling

Supplementary files

Article information

Article type
Paper
Submitted
18 Jul 2019
Accepted
06 Sep 2019
First published
18 Sep 2019

Dalton Trans., 2019,48, 14516-14529

Palladium complexes of N-heterocyclic carbenes displaying an unsymmetrical N-alkylfluorenyl/N′-aryl substitution pattern and their behaviour in Suzuki–Miyaura cross coupling

H. Almallah, E. Brenner, D. Matt, J. Harrowfield, M. Jahjah and A. Hijazi, Dalton Trans., 2019, 48, 14516 DOI: 10.1039/C9DT02948F

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