Reactivity of Tantalum/Iridium and Hafnium/Iridium Alkyl Hydrides with Alkyl Lithium Reagents: Nucleophilic Addition, Alpha-H Abstraction, or Hydride Deprotonation?

International audienceCp*IrH 4 reacts with Hf(Np) 4 (Np = CH 2 C(CH 3) 3) to yield the heterobimetallic complex [Hf(Np) 3 (μ-H) 3 IrCp*], 2. Treatment of 2 with neopentyl lithium (NpLi) results in the nucleophilic addition of a neopentyl moiety onto the Hf center, restoring Hf(Np) 4 and displacing the Cp*IrH 3 iridate fragment. By contrast, treatment of the tantalum/iridium analogue, [Ta(Np) 3 IrH 2 (Cp*)], 1, with NpLi triggers the α-hydrogen abstraction at a Ta-neopentyl moiety and leads to the formation of the alkylidene-ate complex [Li][{Ta(CH t Bu)(Np) 2 }{IrH 2 Cp*}], 4. The benzylidene analogue, [K][{Ta(CHPh)(Np) 2 }{IrH 2 Cp*}], 5, is obtained upon reacting 1 with benzyl potassium. An unusual vinyl oxo species, [{Li(THF) 3 }Ta(O)(Np) 2 {μ-C 2 H 3 }IrH(Cp*)], 6, is formed when the reaction of 1 with NpLi is carried out in THF, due to THF fragmentation