The dehydrotropylium–Co2(CO)6 ion was generated by the action of HBF4 or BF3⋅OEt2 on the corresponding cycloheptadienynol complex, which in turn has been prepared in four steps from a known diacetoxycycloheptenyne complex. The reaction of the cycloheptadienynol complex via the dehydrotropylium–Co2(CO)6 ion with several nucleophiles results in substitution reactions with reactive nucleophiles (N\u3e1) under normal conditions, and a radical dimerisation reaction in the presence of less reactive nucleophiles. Competitive reactions of the cycloheptadienynol complex with an acyclic trienynol complex show no preference for generation of the dehydrotropylium–Co2(CO)6 ion over an acyclic cation. DFT studies on the dehydrotropylium–Co2(CO)6 ion, specifically evaluation of its harmonic oscillator model of aromaticity (HOMA) value (+0.95), its homodesmotic-reaction-based stabilisation energy (≈2.8 kcal mol−1) and its NICS(1) value (−2.9), taken together with the experimental studies suggest that the dehydrotropylium–Co2(CO)6 ion is weakly aromatic
