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

Cp*IrH4 reacts with Hf(Np)4 (Np = CH2C(CH3)3) to yield the heterobimetallic complex [Hf(Np)3(μ-H)3IrCp*], 2. Treatment of 2 neopentyl lithium (NpLi) results in nucleophilic addition a moiety onto Hf center, restoring and displacing Cp*IrH3– iridate fragment. By contrast, treatment tantalum/iridium analogue [Ta(Np)3IrH2(Cp*)], 1, NpLi triggers α-hydrogen abstraction at Ta–neopentyl leads formation alkylidene -ate [Li][{Ta(CHtBu)(Np)2}{IrH2Cp*}], 4. The benzylidene [K][{Ta(CHPh)(Np)2}{IrH2Cp*}], 5, is obtained upon reacting 1 benzyl potassium. An unusual vinyl oxo species, [{Li(THF)3}Ta(O)(Np)2{μ-C2H3}IrH(Cp*)], 6, formed when reaction carried out tetrahydrofuran (THF) due THF fragmentation.