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Structural characterisation of solution species implicated in the palladium-catalysed Heck reaction by Pd K-edge X-ray absorption spectroscopy: palladium acetate as a catalyst precursor

Structural characterisation of solution species implicated in the palladium-catalysed Heck reaction by Pd K-edge X-ray absorption spectroscopy: palladium acetate as a catalyst precursor
Structural characterisation of solution species implicated in the palladium-catalysed Heck reaction by Pd K-edge X-ray absorption spectroscopy: palladium acetate as a catalyst precursor
Energy dispersive EXAFS (EDE), Quick EXAFS (QEXAFS), C-13 NMR and X-ray crystallography have been used to probe the co-ordination sphere of palladium in the course of the phosphine free Heck reaction. [Pd2I6][NBu3H](2) has been isolated from the precatalytic solution and its crystal structure determined. EDE and QEXAFS spectra of the complexes Pd(OAc)(2), Pd(PPh3)(4) and [Pd2I6][NEt3H](2) illustrated the value of the technique in structure elucidation. EXAFS of the precatalytic solution detects [Pd2I6](2-) and no co-ordinated carbon. EXAFS of the catalytic solution shows a first co-ordination sphere of 2 carbon atoms and a second of 2-2.5 iodines. A scheme involving an equilibrium between the oxidative addition product and the olefin co-ordination species, has been proposed to explain these results.
alkene oligomerization catalyst, homogeneous nickel-catalysts, zerovalent palladium, oxidative addition, crystal-structure, in-situ, aromatic iodides, complexes, exafs, mechanism
1472-7773
2207-2212
Evans, John
05890433-0155-49fe-a65d-38c90ea25c69
O'Neill, Lynn
81f220a6-f33c-4a0a-a48f-ec920c746007
Kambhampati, Vijaya L.
e2e742f5-1a6a-4e94-bc27-1af0517aec7f
Rayner, Graham
60562524-1437-47ec-a5b2-c2619e855dff
Turin, Sandra
6691348e-e3e2-4afb-8384-131a363a07d0
Genge, Anthony
c549244e-52bc-444c-a33d-34b96360b0f3
Dent, Andrew J.
24c2a218-cb0e-4193-af0b-3ff1dc42b552
Neisius, Thomas
22f85c0b-ae48-41ca-87f0-34ec82d2b496
Evans, John
05890433-0155-49fe-a65d-38c90ea25c69
O'Neill, Lynn
81f220a6-f33c-4a0a-a48f-ec920c746007
Kambhampati, Vijaya L.
e2e742f5-1a6a-4e94-bc27-1af0517aec7f
Rayner, Graham
60562524-1437-47ec-a5b2-c2619e855dff
Turin, Sandra
6691348e-e3e2-4afb-8384-131a363a07d0
Genge, Anthony
c549244e-52bc-444c-a33d-34b96360b0f3
Dent, Andrew J.
24c2a218-cb0e-4193-af0b-3ff1dc42b552
Neisius, Thomas
22f85c0b-ae48-41ca-87f0-34ec82d2b496

Evans, John, O'Neill, Lynn, Kambhampati, Vijaya L., Rayner, Graham, Turin, Sandra, Genge, Anthony, Dent, Andrew J. and Neisius, Thomas (2002) Structural characterisation of solution species implicated in the palladium-catalysed Heck reaction by Pd K-edge X-ray absorption spectroscopy: palladium acetate as a catalyst precursor. Journal of the Chemical Society, Dalton Transactions, (10), 2207-2212. (doi:10.1039/b200617k).

Record type: Article

Abstract

Energy dispersive EXAFS (EDE), Quick EXAFS (QEXAFS), C-13 NMR and X-ray crystallography have been used to probe the co-ordination sphere of palladium in the course of the phosphine free Heck reaction. [Pd2I6][NBu3H](2) has been isolated from the precatalytic solution and its crystal structure determined. EDE and QEXAFS spectra of the complexes Pd(OAc)(2), Pd(PPh3)(4) and [Pd2I6][NEt3H](2) illustrated the value of the technique in structure elucidation. EXAFS of the precatalytic solution detects [Pd2I6](2-) and no co-ordinated carbon. EXAFS of the catalytic solution shows a first co-ordination sphere of 2 carbon atoms and a second of 2-2.5 iodines. A scheme involving an equilibrium between the oxidative addition product and the olefin co-ordination species, has been proposed to explain these results.

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More information

Published date: 2002
Keywords: alkene oligomerization catalyst, homogeneous nickel-catalysts, zerovalent palladium, oxidative addition, crystal-structure, in-situ, aromatic iodides, complexes, exafs, mechanism

Identifiers

Local EPrints ID: 19729
URI: http://eprints.soton.ac.uk/id/eprint/19729
ISSN: 1472-7773
PURE UUID: fcf241c0-e3b3-42e5-9150-9a128c2c4a8e

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Date deposited: 17 Feb 2006
Last modified: 15 Jul 2019 19:26

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