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Issue 21, 2004
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Synthesis, structure and reactivity of palladium(ii) complexes of chiral N-heterocyclic carbene–imine and –amine hybrid ligands

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Abstract

The synthesis and structures of chiral N-heterocyclic carbene (NHC)–N-donor complexes of silver(I) and palladium(II) are reported. The X-ray structure of an NHC–imine silver(I) complex [(nPrCNCHPh)AgBr] (2) exhibits an Ag2Br2 dimer motif where the imine group is not coordinated to the silver atom. Reaction between 2 and [PdCl2(MeCN)2] gives the palladium(II) complex [(κ2-nPrCNCHPh)PdCl2] (3) that contains a chelating NHC–imine ligand as shown by single-crystal X-ray diffraction. Slow hydrolysis of related complexes [(κ2-nPrCNCHPh)PdCl2] (3) and [(κ2-(Ph)2CHCNCHPh)PdCl2] (4) using triethylammonium chloride and water lead to the precipitation of single crystals of insoluble NHC–amino palladium(II) complexes [(κ2-nPrCNH2)PdCl2] (6) and [(κ2-(Ph)2CHCNH2)PdCl2] (7), respectively. In the solid state, complexes 6 and 7 both exhibit intermolecular hydrogen bonding between chlorine and an amino–hydrogen atom resulting in an infinite chain structure. Substitution of an amino hydrogen for an ethyl group gives the soluble complex [(κ2-iPrCN(H)Et)PdCl2] (12). Reaction between two equivalents of 2 and [PdCl2(MeCN)2] gives the di-NHC complex [(κ1-nPrCNCHPh)2PdCl2] (5) that does not contain a coordinated imine as shown by single crystal X-ray diffraction. Conproportionation between 5 and an equivalent of [PdCl2(MeCN)2] to 3 does not occur at temperatures up to 100 °C in CD3CN.

Graphical abstract: Synthesis, structure and reactivity of palladium(ii) complexes of chiral N-heterocyclic carbene–imine and –amine hybrid ligands

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Article information


Submitted
07 Jun 2004
Accepted
14 Sep 2004
First published
29 Sep 2004

Dalton Trans., 2004, 3528-3535
Article type
Paper

Synthesis, structure and reactivity of palladium(II) complexes of chiral N-heterocyclic carbeneimine and –amine hybrid ligands

L. G. Bonnet, R. E. Douthwaite, R. Hodgson, J. Houghton, B. M. Kariuki and S. Simonovic, Dalton Trans., 2004, 3528
DOI: 10.1039/B408594A

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