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Issue 19, 2011
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Cyclopropenylidenecarbeneligands in palladium catalysed coupling reactions: carbeneligand 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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Supplementary files

Article information


Submitted
19 Jan 2011
Accepted
18 Feb 2011
First published
07 Apr 2011

Dalton Trans., 2011,40, 5316-5323
Article type
Paper

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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