Silylpalladium Cations Enable the Oxidative Addition of C(sp³)–O Bonds

The synthesis and characterization of the room-temperature and solution-stable silylpalladium cations (PCy3)2Pd–SiR3+(C6F5)4B– (SiR3 = SiMe2Et, SiHEt2) and (Xantphos)­Pd–SiR3+(BArf4) (SiR3 = SiMe2Et, SiHEt2; Xantphos = 4,5-bis­(diphenylphosphino)-9,9-dimethylxanthene; BArf4 = (3,5-(CF3)2C6H3)4B–) are reported. Spectroscopic and ligand addition experiments suggest that silylpalladium complexes of the type (PCy3)2Pd–SiR3+ are three-coordinate and T-shaped. Addition of dialkyl ethers to both the PCy3 and Xantphos-based silylpalladium cations resulted in the cleavage of C­(sp3)–O bonds and the generation of cationic Pd–alkyl complexes. Mechanistically enabling is the ability of silylpalladium cations to behave as sources of both electrophilic silylium ions and nucleophilic LnPd­(0).本文报道了室温稳定且溶液中稳定的甲硅烷基钯阳离子（silylpalladium cations）配合物的合成与表征，涵盖两类体系：(PCy3，三环己基膦)₂Pd–SiR₃⁺(C₆F₅)₄B⁻ [SiR₃ = SiMe₂Et、SiHEt₂]，以及(Xantphos，即4,5-双(二苯基膦基)-9,9-二甲基氧杂蒽)Pd–SiR₃⁺(BArf4，即(3,5-(CF₃)₂C₆H₃)₄B⁻) [SiR₃ = SiMe₂Et、SiHEt₂]。光谱表征与配体加成实验结果表明，(PCy3)₂Pd–SiR₃⁺型甲硅烷基钯配合物为三配位T形结构。向基于PCy3与Xantphos的甲硅烷基钯阳离子体系中添加二烷基醚时，可发生C(sp³)–O键断裂，并生成阳离子型钯烷基配合物。该反应的机理核心在于，甲硅烷基钯阳离子可同时作为亲电甲硅鎓离子（silylium ions）与亲核LnPd(0)的来源。