Issue 10, 2009

Iridium complexes of N-heterocyclic carbenes in C–H borylation using energy efficient microwave technology: influence of structure, ligand donor strength and counter ion on catalytic activity

Abstract

Bridged and unbridged N-heterocyclic carbene (NHC) ligands were metalated with [Ir(COD)Cl]2 to give iridium(I) mono- and biscarbene substituted catalysts [Ir(COD)NHC(Cl)] and [Ir(COD)(NHC)2][X] (X: I, PF6, BF4, CF3COO, OTf). The prepared NHC-complexes were tested in the C–H borylation reaction of aromatic carbons with bis(pinacolato)diboron (B2pin2) and pinacolborane (HBpin). The use of microwave technology in this study not only facilitates a time efficient screening of a wide range of influences such as ligand σ-donor strength and structural motif as well as the effects of the complex counter ion, but also provides an energy efficient heating source. Catalyst 6TFA, which features a chelating NHC ligand, proved to be most effective catalyst and further investigations with this complex in the borylation of mono- and disubstituted benzene derivatives exploring chemo- and regioselectivity were undertaken.

Graphical abstract: Iridium complexes of N-heterocyclic carbenes in C–H borylation using energy efficient microwave technology: influence of structure, ligand donor strength and counter ion on catalytic activity

Supplementary files

Article information

Article type
Paper
Submitted
15 Apr 2009
Accepted
19 Jun 2009
First published
22 Jul 2009

Green Chem., 2009,11, 1610-1617

Iridium complexes of N-heterocyclic carbenes in C–H borylation using energy efficient microwave technology: influence of structure, ligand donor strength and counter ion on catalytic activity

C. F. Rentzsch, E. Tosh, W. A. Herrmann and F. E. Kühn, Green Chem., 2009, 11, 1610 DOI: 10.1039/B913055C

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