Arylmagnesium to arylcopper conversion monitored by solid state characterization of halide intermediates. Synthesis of homoleptic (o-vinylphenyl)copper

The reaction between Mg(viph)(2) (viph = o-vinylphenyl) and copper(I) chloride has been found to be the best way of preparing the homoleptic tetramer [Cu-4(viph)(4)]. The MgR(2) reagent crystallizes as monomeric [Mg(THF)(2)(viph)(2)] from a THF solution. In the reaction between the Grignard reagent (viph)MgBr and copper(I) chloride, two unstable mixed halide/aryl intermediates, [Mg(THF)(6)][Cu-5(viph)(2)Br-4](2) . THF (3) and [Mg(THF)(5)Cl][Cu-5(viph)(4)Br-2].-THF (4), were isolated and found to reduce the yield of [Cu-4(viph)(4)] markedly. The crystal structures of 3 and 4 were determined and were found to exhibit unusual coordination geometries for copper(I) and provide mechanistic information. Compound 3 was found to react with excess triphenylphosphine in THF, yielding [Cu(PPh(3))(3)Br]. THF. It is suggested that [Cu-4(viph)(4)], which is not pi-coordinated in the solid state or in THF solution, may have important precursor qualities for the preparation of new organocopper compounds.