Synthetic, Structural, and Mechanistic studies on the oxidative addition of Aromatic Chlorides to a palladium (N-heterocyclic carbene) complex: Relevance to catalytic amination

Lewis, Alexandra K de K, Caddick, Stephen, Cloke, F Geoffrey N, Billingham, Norman C, Hitchcock, Peter B and Leonard, John (2003) Synthetic, Structural, and Mechanistic studies on the oxidative addition of Aromatic Chlorides to a palladium (N-heterocyclic carbene) complex: Relevance to catalytic amination. Journal of the American Chemical Society, 125 (33). pp. 10066-10073. ISSN 0002-7863

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Abstract

The oxidative addition products trans-[Pd(NHC)(2)(Ar)Cl] (NHC = cyclo-C{(NBuCH)-Bu-I}(2); Ar = Me-4-C6H4, MeO-4-C6H4, CO2Me-4-C6H4) have been isolated in good yields from the reactions of ArCl with the amination precatalyst [Pd(NHC)(2)] and structurally characterized. The former undergo reversible dissociation of one NHC ligand at elevated temperatures, and a value of 25.57 kcal mol(-1) has been determined for the Pd-NHC dissociation enthalpy in the case where Ar = Me-4-C6H4. Detailed kinetic studies have established that the oxidative addition reactions proceed by a dissociative mechanism. Rate data for the oxidation addition of Me-4-C6H4Cl to [Pd(NHC)(2)] compared to that obtained for the [Pd(NHC)(2)]-catalyzed coupling of morpholine with 4-chlorotoluene are consistent with a rate-determining oxidative addition in the catalytic amination reaction. The relative rates of oxidative addition of the three aryl chlorides to [Pd(NHC)(2)] (CO2Me-4-C6H4Cl > Me-4-C6H4Cl > MeO-4-C6H4Cl) reflect the electronic nature of the substituents and also parallel observed trends in coupling efficiency for these aryl halides in aminations.

Item Type: Article
Additional Information: Times Cited: 17; Keywords: HECK-TYPE REACTIONS; COUPLING REACTIONS; ARYL CHLORIDES; C-C; HALIDES; REACTIVITY; LIGANDISI:000184779100041 Other internal authors: Peter Hichcock
Schools and Departments: School of Life Sciences > Chemistry
Depositing User: Alex Lewis
Date Deposited: 06 Feb 2012 19:58
Last Modified: 30 Nov 2012 17:05
URI: http://sro.sussex.ac.uk/id/eprint/23264
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