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Issue 19, 2011
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Cyclopropenylidene carbene ligands in palladium catalysed coupling reactions: carbene ligand rotation and application to the Stille reaction

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Abstract

Reaction of [Pd(PPh3)4] with 1,1-dichloro-2,3-diarylcyclopropenes gives complexes of the type cis-[PdCl2(PPh3)(C3(Ar)2)] (Ar = Ph 5, Mes 6). Reaction of [Pd(dba)2] with 1,1-dichloro-2,3-diarylcyclopropenes in benzene gave the corresponding binuclear palladium complexes trans-[PdCl2(C3(Ar)2)]2 (Ar = Ph 7, p-(OMe)C6H48, p-(F)C6H49). Alternatively, when the reactions were performed in acetonitrile, the complexes trans-[PdCl2(NCMe)(C3(Ar)2)] (Ar = Ph 10, p-(OMe)C6H411 and p-(F)C6H4) 12) were isolated. Addition of phosphine ligands to the binuclear palladium complex 7 or acetonitrile adducts 11 and 12 gave complexes of the type cis-[PdCl2(PR3)(C3(Ar)2)] (Ar = Ph, R = Cy 13, Ar = p-(OMe)C6H4, R = Ph 14, Ar = p-(F)C6H4, R = Ph 15). Crystal structures of complexes 6·3.25CHCl3, 10, 11·H2O and 12–15 are reported. DFT calculations of complexes 10–12 indicate the barrier to rotation about the carbene-palladium bond is very low, suggesting limited double bond character in these species. Complexes 5–9 were tested for catalytic activity in C–C coupling (Mizoroki–Heck, Suzuki–Miyaura and, for the first time, Stille reactions) and C–N coupling (Buchwald–Hartwig amination) showing excellent conversion with moderate to high selectivity.

Graphical abstract: Cyclopropenylidene carbene ligands in palladium catalysed coupling reactions: carbene ligand rotation and application to the Stille reaction

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Publication details

The article was received on 19 Jan 2011, accepted on 18 Feb 2011 and first published on 07 Apr 2011


Article type: Paper
DOI: 10.1039/C1DT10109A
Citation: Dalton Trans., 2011,40, 5316-5323
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    Cyclopropenylidene carbene ligands in palladium catalysed coupling reactions: carbene ligand rotation and application to the Stille reaction

    R. Chotima, T. Dale, M. Green, T. W. Hey, C. L. McMullin, A. Nunns, A. Guy Orpen, I. V. Shishkov, D. F. Wass and R. L. Wingad, Dalton Trans., 2011, 40, 5316
    DOI: 10.1039/C1DT10109A

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