Formation of a Hexanuclear Octatetraenyl Organocopper(I) Aggregate via Oxidation of Spiro Butadienyl Organocuprate

Spiro butadienyl tetraorganocuprates 2a,b were synthesized from butadienyl dilithio reagent and 0.5 equiv of copper(I) salt. The oxidation reaction of 2a,b with I2 or p-benzoquinone afforded the octatetraenyl organocopper(I) aggregate 3. This result demonstrated that the butadienyl skeletons rather than the copper(I) atom were oxidized preferentially. Single-crystal X-ray structural analysis revealed that the high-order organocuprates 2a,b have linear or zigzag polymeric structures, while the hexanuclear octatetraenyl organocopper(I) aggregate 3 consists of a core Cu6 structure, which forms a regular hexagon.