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 π-coordinated in the solid state or in THF solution, may have important precursor qualities for the preparation of new organocopper compounds.