Annelation of ring-opened arylcyclopropenium ions to co-ordinated cyclo-octatetraene, and the X-ray crystal structure of [Fe(CO)3(σ,η3-C11H9Ph3)]

The cycle-octatetraene (cot) complexes [M(CO)3(η4-cot)](M = Fe or Ru) undergo electrophilic addition reactions with arylcyclopropenium ions as their [BF4]– salts, [C3Ph2R][BF4](R = H or Ph), togive [M(CO)3(η2:η3-C11H8Ph2R)][BF4](1; M = Fe or Ru, R = H or Ph); hydride addition to (1; M = Fe, R = Ph) yields [Fe(CO)3(σ,η3-C11H9Ph3)](2). The X-ray structure of compound (2) shows the ring-opened cyclopropenium ion to be bonded to the original cot ring via three new carbon–carbon bonds. The resulting polycyclic hydrocarbon ligand is attached to the iron atom by a σ,η3-bonded eight-membered ring, and also contains substituted cyclopentene, cyclohexane, and cyclohexenyl moieties. Complex (2) crystallises in the monoclinic space group P21/n, and the structure has been refined to R(R′)= 0.073 (0.077) for 2 484 reflections [I 3.0σ(I)].