New Highly Stable Metallabenzenes via Nucleophilic Aromatic Substitution Reaction

摘要

Treatment of the ruthenabenzene [Ru{CHC(PPh₃)CHC(PPh₃)CH}Cl₂(PPh₃)₂]Cl (1) with excess 8-hydroxyquinoline in the presence of CH₃COONa under air atmosphere produced the S_NAr product [(C₉H₆NO)Ru{CHC(PPh₃)CHC(PPh₃)C}(C₉H₆NO)(PPh₃)]Cl₂ (3). Ruthenabenzene 3 could be stable in the solution of weak alkali or weak acid. However, reaction of 3 with NaOH afforded a 7:1 mixture of ruthenabenzenes [(C₉H₆NO)Ru{CHC(PPh₃)CHCHC}(C₉H₆NO)(PPh₃)]Cl (4) and [(C₉H₆NO)Ru{CHCHCHC(PPh₃)C}(C₉H₆NO)(PPh₃)]Cl (5), presumably involving a PC bond cleavage of the metallacycle. Complex 3 was also reactive to HCl, which results in a transformation of 3 to ruthenabenzene [Ru{CHC(PPh₃)CHC(PPh₃)C}Cl₂(C₉H₆NO)(PPh₃)]Cl (6) in high yield. Thermal stability tests showed that ruthenabenzenes 4, 5, and 6 have remarkable thermal stability both in solid state and in solution under air atmosphere. Ruthenabenzenes 4 and 5 were found to be fluorescent in common solvents and have spectral behaviors comparable to those organic multicyclic compounds containing large π-extended systems.