A new highly active diphosphane-palladium(II) complex as a catalyst precursor for the Heck reaction

The new diphosphane ligand cis-1,3-bis[(diphenylphosphanyl)methyl]cyclohexa ne (4) has been prepared and has allowed the synthesis of the palladium com plex cis-[Pd(4)(CO2CF3)(2)] (6). To obtain cis complexation of the diphosph ane in 6 the cyclohexane skeleton adopts a chair conformation with a diaxia l orientation of the substituents, a structure that has been verified by an X-ray structure determination. This complex efficiently catalyses the viny lation of iodo- and bromobenzenes in high yields. For the best reaction, wi th methyl acrylate and iodobenzene, a yield of > 98% was obtained with an a verage turnover frequency of 11 760 h(-1) and a turnover number of 1 176 00 0.