Iminophosphine-palladium(0) complexes as catalysts for the Stille reaction.

The cross-coupling of iodobenzene with tributylphenylethynylstannane or tributylvinylstannane is efficiently catalysed by iminophosphine–palladium(0)–olefin complexes of the type [Pd(h2-dmf)(P-N)] (dmf, dimethylfumarate; P-N, 1-(PPh2)-C6H4-2-CvNR (R¼alkyl, aryl)). The catalytic activity depends on the R substituent of the imino group: the highest reaction rates are obtained using arylsubstituted iminophosphines. Equivalent catalytic systems can be obtained using a palladium source such as Pd(OAc)2 or Pd(dba)2(dibenzylideneacetone, dba) in combination with the iminophosphine ligands. In the coupling of iodobenzene with tributylphenylethynylstannane, the highest reaction rates are obtained using an iminophosphine/palladium molar ratio of 2:1, while in the vinylstannane–iodobenzene coupling the best P-N/Pd ratio is 1:1.