The [RPPh₃]₂[Pd₂X₆] as a Catalyst Precursor for the Heck Cross-Coupling Reaction by in situ Formation of Stabilized Pd(0) Nanoparticles

Abstract

Pd(II) anionic, square planar complexes of the type [RPPh₃]₂[Pd₂X₂Cl₄], where X = Cl, Br, have been applied for the first time as a catalyst precursor for the Heck reaction carried out in DMF at 140 °C. The highest yield was obtained for the most reducible ones, [MePPh₃]₂[Pd₂Br₂Cl₄], in DMF in the presence of NaHCO₃ as a base. It was found that during the reaction, phosphonium halide stabilized Pd(0) nanoparticles of about 10 nm, which have been formed in situ from the palladium(II) precursor and Pd(0) colloidal nanoparticles acts as the reservoir for Pd(II) species via activation of the metal surface through the oxidative addition of aryl halides.

Key words

olefination - arylation - catalysis - palladium - nano­structures

• References and Notes

• 1 Littke AF, Fu GC. J. Am. Chem. Soc. 2001; 123: 6989
• 2 Consorti CS, Flores FR, Dupont J. J. Am. Chem. Soc. 2005; 127: 12054
• 3 Schils D, Stappers F, Solberghe G, van Heck R, Coppens M, Van den Heuvel D, Van der Donck P, Callewaert T, Meeussen F, Bie ED, Eersels K, Schouteden E. Org. Process Res. Dev. 2008; 12: 530
• 4 Bouquillon S, du Moulinet d’Hardemare A, Averbuch-Pouchot M.-T, Hénin F, Muzart J. Polyhedron 1999; 18: 3511
• 5 Dullius JE. L, Suarez PA. Z, Einloft S, de Souza RF, Dupont J, Fischer J, De Cian A. Organometallics 1998; 17: 815
• 6 Zawartka W, Gniewek A, Trzeciaka AM, Ziłkowski JJ, Pernak J. J. Mol. Catal. A: Chem. 2009; 304: 8
• 7 Zawartka W, Trzeciak AM, Ziłkowski JJ, Lis T, Ciunik Z, Pernak J. Adv. Synth. Catal. 2006; 348: 1689
• 8 Baig S, Richard B, Serp P, Mijoule l, Hussein K, Guihéry N, Barthelat J, Kalck P. Inorg. Chem. 2006; 45: 1935
• 9 Makitova DD, Krasochka ON, Atovmyan LO, Letuchii YA, Roshchupkina OS. Coord. Chem. (Engl. Transl.) 1987; 13: 928
• 10 Kaufmann DE, Nouroozian M, Henze H. Synlett 1996; 1091
• 11 Gerritsma DA, Robertson A, McNulty J, Capretta A. Tetrahedron Lett. 2004; 45: 7629
• 12 Bhattacharya S, Srivastava A, Sengupta S. Tetrahedron Lett. 2005; 46: 3557
• 13 Precht MH. G, Scholten JD, Dupont J. Molecules 2010; 15: 3441
• 14 Typical Procedure for the Heck Arylation of Aryl Halides with Methyl Acrylate: Palladium complex ([MePPh₃]₂[Pd₂Br₂Cl₄]) (0.01 mmol), methyl acrylate (0.5 mmol), aryl halides (0.25 mmol), NaHCO₃ (0.5 mmol) and DMF (1.5 mL) were added to a 5-mL round-bottomed flask equipped with an efficient condenser and stirred at 140 °C in an oil bath for the time specified in Table 3. The course of the reaction was monitored by periodically taking samples and analyzing them by means of GC analysis. After cooling of the reaction mixture to r.t., the aqueous solution was extracted with hexane, the organic phase was dried over MgSO₄, and the solvent was then removed under vacuum. Column chromatography on silica gel afforded the desired product. The product was characterized by ¹H NMR and IR.