Coordination studies of polycondensed π-perimeters: mono-, di- and tri-nuclear cobalt sandwich complexes of tetracene, benzo[a]pyrene, triphenylene, benzo[b]triphenylene and perylene

By means of arene ligand exchange of the triple deckers [{(η5-R1–5C5)Co}2-μ-(η4:η4-toluene)] (R1–5=Me, R1–3=tert-butyl) at room temperature a number of mono-, di-, and tri-nuclear sandwich complexes of the polycondensed aromatics polycyclic aromatic hydrocarbons (PAHs) tetracene, benzo[a]pyrene, perylene, triphenylene and benzo[a]triphenylene have been synthesized. For triphenylene and benzo[b]triphenylene however, a threefold coordination of [(η5-C5Me5)Co] fragments in the periphery of these PAHs is found, tetracene allows for a twofold coordination of two [(η5-C5Me5)Co] fragments in the ring periphery leaving a central naphthalene unit of this PAH uncomplexed. Perylene serves as a twofold coordination site for [(η5-1,2,4 tri-tert-butyl-C5H2)Co] fragments which are coordinated in each of the two naphthalene fragments of this π-perimeter.