Nucleophilic Aromatic Addition Reactions of the Metallabenzenes and Metallapyridinium: Attacking Aromatic Metallacycles with Bis(diphenylphosphino)methane to Form Metallacyclohexadienes and Cyclic η2-Allene-Coordinated Complexes

摘要

The reactions of phosphonium-substituted metallabenzenes and metallapyridinium with bis(diphenylphosphino)methane (DPPM) were investigated. Treatment of [Os{CHC(PPh₃)CHC(PPh₃)CH}Cl₂(PPh₃)₂]Cl with DPPM produced osmabenzenes [Os{CHC(PPh₃)CHC(PPh₃)CH}Cl₂{(PPh₂)CH₂(PPh₂)}]Cl (2), [Os{CHC(PPh₃)CHC(PPh₃)CH}Cl{(PPh₂)CH₂(PPh₂)}₂]Cl₂ (3), and cyclic osmium η2-allene complex [Os{CHC(PPh₃)CH(η2-CCH)}Cl₂{(PPh₂)CH₂(PPh₂)}₂]Cl (4). When the analogue complex of osmabenzene 1, ruthenabenzene [Ru{CHC(PPh₃)CHC(PPh₃)CH}Cl₂(PPh₃)₂]Cl, was used, the reaction produced ruthenacyclohexadiene [Ru{CHC(PPh₃)CHC(PPh₃)CH}Cl{(PPh₂)CH₂(PPh₂)}₂]Cl₂ (6), which could be viewed as a Jackson–Meisenheimer complex. Complex 6 is unstable in solution and can easily be convert to the cyclic ruthenium η2-allene complexes [Ru{CHC(PPh₃)CH(η2-CCH)}Cl{(PPh₂)CH₂(PPh₂)}₂]Cl₂ (7) and [Ru{CHC(PPh₃)CH(η2-CCH)}Cl₂{(PPh₂)CH₂(PPh₂)}₂]Cl (8). The key intermediates of the reactions have been isolated and fully characterized, further supporting the proposed mechanism for the reactions. Similar reactions also occurred in phosphonium-substituted metallapyridinium [OsCl₂{NHC(CH₃)C(Ph)C(PPh₃)CH}(PPh₃)₂]BF₄ to give the cyclic osmium η2-allene-imine complex [OsCl₂{NHC(CH₃)C(Ph)(η2-CCH)}{(PPh₂)CH₂(PPh₂)}(PPh₃)]BF₄ (11).