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 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*IrH3– iridate fragment. By contrast, treatment of the tantalum/iridium analogue [Ta­(Np)3IrH2(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(CHtBu)­(Np)2}­{IrH2Cp*}], 4. The benzylidene analogue [K]­[{Ta­(CHPh)­(Np)2}­{IrH2Cp*}], 5, is obtained upon reacting 1 with benzyl potassium. An unusual vinyl oxo species, [{Li­(THF)3}­Ta­(O)­(Np)2{μ-C2H3}­IrH­(Cp*)], 6, is formed when the reaction of 1 with NpLi is carried out in tetrahydrofuran (THF) due to THF fragmentation.

Cp*IrH4（五甲基环戊二烯基四氢化铱，Cp*IrH4）与Hf(Np)4发生反应，其中Np代表CH₂C(CH₃)₃（新戊基，neopentyl），可生成异双金属配合物[Hf(Np)₃(μ-H)₃IrCp*]，记为化合物2。采用新戊基锂（neopentyl lithium，NpLi）处理化合物2时，新戊基片段会亲核加成至铪中心，再生得到Hf(Np)4，并置换出Cp*IrH₃⁻铱酸盐片段。与之形成对照的是，用NpLi处理钽/铱的类似物[Ta(Np)₃IrH₂(Cp*)]（记为化合物1）时，会触发Ta-新戊基片段的α-氢抽提反应，最终生成亚烷基-ate型配合物[Li][{Ta(CHtBu)(Np)₂}{IrH₂Cp*}]，即化合物4。将化合物1与苄基钾反应，可得到其亚苄基类似物[K][{Ta(CHPh)(Np)₂}{IrH₂Cp*}]，即化合物5。当化合物1与NpLi在四氢呋喃（tetrahydrofuran，THF）中进行反应时，因THF发生断裂碎裂，会生成一种罕见的乙烯基氧物种[{Li(THF)₃}Ta(O)(Np)₂{μ-C₂H₃}IrH(Cp*)]，即化合物6。