Unexpected -to- Isomerizations during the Negishi-Type Homocoupling of Iodoalkenes.

The direct insertion of Zn into olefin-halide bonds is a challenge. When ()-alkenyl iodides were treated with a very large excess of Zn nanoparticles, in the presence of Pd(PPh), the dimerization was observed but, unexpectedly, yielding mainly -1,3-dienes. This apparently contrathermodynamic -to- isomerization of organometallic intermediates is predicted to be general and is explained with the aid of DFT [principally M06/6-311+G(d,p)], MP2, and CCSD(T) calculations.