Issue 28, 2007

Structural variation, dynamics, and catalytic application of palladium(ii) complexes of di-N-heterocyclic carbene–amine ligands

Abstract

A series of palladium(II) complexes incorporating di-NHC–amine ligands has been prepared and their structural, dynamic and catalytic behaviour investigated. The complexes [trans-(κ2-tBuCN(Bn)CtBu)PdCl2] (12) and [trans-(κ2-MesCN(H)CMes)PdCl2] (13) do not exhibit interaction between the amine nitrogen and palladium atom respectively. NMR spectroscopy between −40 and 25 °C shows that the di-NHC–amine ligand is flexible expressing Cs symmetry and for 13 rotation of the mesityl groups is prevented. In the related C1 complex [(κ3-tBuCN(H)CtBu)PdCl][Cl] (14) coordination of NHC moieties and amine nitrogen atom is observed between −40 and 25 °C. Reaction between 12–14 and two equivalents of AgBF4 in acetonitrile gives the analogous complexes [trans-(κ2-tBuCN(Bn)CtBu)Pd(MeCN)2][BF4]2 (15), [trans-(κ2-MesCN(H)CMes)Pd(MeCN)2][BF4]2 (16) and [(κ3-tBuCN(H)CtBu)Pd(MeCN)][BF4]2 (17) indicating that ligand structure determines amine coordination. The single crystal X-ray structures of 12, 17 and two ligand imidazolium salt precursors tBuC(H)N(Bn)C(H)tBu][Cl]2 (2) and [tBuC(H)N(H)C(H)tBu][BPh4]2 (4) have been determined. Complexes 12–14 and 15–17 have been shown to be active precatalysts for Heck and hydroamination reactions respectively.

Graphical abstract: Structural variation, dynamics, and catalytic application of palladium(ii) complexes of di-N-heterocyclic carbene–amine ligands

Supplementary files

Article information

Article type
Paper
Submitted
05 Mar 2007
Accepted
23 Apr 2007
First published
17 May 2007

Dalton Trans., 2007, 3065-3073

Structural variation, dynamics, and catalytic application of palladium(II) complexes of di-N-heterocyclic carbeneamine ligands

J. Houghton, G. Dyson, R. E. Douthwaite, A. C. Whitwood and B. M. Kariuki, Dalton Trans., 2007, 3065 DOI: 10.1039/B703248J

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