Synthesis and Explosive Decomposition of Organometallic Dehydro[18]annulenes:  An Access to Carbon Nanostructures

The synthesis of eight new cyclobutadiene or ferrocene-fused organometallic dehydroannulenes is reported. Cadiot-type coupling of a 1-bromoethynyl-2-silylethynylbenzene derivative to an organometallic diyne (1,2-diethynyl-3,4-bis(trimethylsilyl)cyclobutadiene(cyclopentadienyl )cobalt or 1,2-diethynylferrocene) is followed by deprotection and Cu(OAc)2-promoted ring closure. Five of the organometallic dehydroannulenes were structurally characterized. Three of the novel cycles explode at temperatures from 196 to 293 °C and form insoluble carbon materials. The soot produced from 13a shows a high abundance of onion-like carbon nanostructures. The nanostructures were characterized by high-resolution transmission electron microscopy.