3854-81-7Relevant academic research and scientific papers
Cyclopropenylidene carbene ligands in palladium catalysed coupling reactions: Carbene ligand rotation and application to the Stille reaction
Chotima, Ratanon,Dale, Tim,Green, Michael,Hey, Thomas W.,McMullin, Claire L.,Nunns, Adam,Guy Orpen,Shishkov, Igor V.,Wass, Duncan F.,Wingad, Richard L.
experimental part, p. 5316 - 5323 (2011/06/27)
Reaction of [Pd(PPh3)4] with 1,1-dichloro-2,3- diarylcyclopropenes gives complexes of the type cis-[PdCl2(PPh 3)(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(C 3(Ar)2)]2 (Ar = Ph 7, p-(OMe)C 6H48, 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-[PdCl 2(PR3)(C3(Ar)2)] (Ar = Ph, R = Cy 13, Ar = p-(OMe)C6H4, R = Ph 14, Ar = p-(F)C 6H4, 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.
