The arene ligand exchange mechanism of slipped arene triple deckers [Bis{(η5-CpR)Co}-μ-{η4:η4-arene}] (R = Me5, 1,2,4 tri-tert butyl, arene = benzene, toluene) 1 was studied by 1H-NMR spectroscopy for different concentrations and solvents. It has been found that triple deckers of type 1 decompose slowly in solution. A unique equilibrium, between these triple deckers and the mixed sandwich complexes [(η6-arene)Co(η5-CpR)] and 14 e [(η5-Cp)Co]solv fragments generated in situ by decomposition o f 1 exists. In addition to this equilibrium arene lability of the thus formed mixed sandwich complex type has been detected by NMR making slipped triple deckers 1 ideal single source compounds for the generation of two [(η5-Cp)Co] fragments in one reaction step. Such fragments are valuable metal ligand components with high synthetic utility in organometallic chemistry.
