New carbon-rich organometallic architectures based on cyclobutadienecyclopentadienylcobalt and ferrocene modules

This review describes the chemistry of alkynylated cyclobutadiene complexes and alkynylated ferrocenes. These complexes are made by a combination of metalation, formylation and Ohira alkynylation. The transformation of a formyl group into an alkyne is a critical step in these syntheses. The use of a diazophosphonate as the source of a carbon atom is convenient and has allowed for the synthesis of a host of alkynylated π-complexes. Multiply alkynylated ferrocenes and cyclobutadiene(cyclopentadienyl)cobalt complexes are utilized as stepping stone for complex carbon-rich organometallics. Half-wheel, butterfly, and similar structures have been accessed and characterized by single crystal X-ray methods. A ferrocene-fused dehydro[18]annulene decomposes explosively when heated above 200 °C with formation of carbon nanostructures that are bagel- or onion-shaped and that have been characterized by electron microscopy. This account as well describes the synthesis and characterization of organometallic dendrimers and conjugated organometallic polymers.