Sterically Encumbered Iridium Bis(N-heterocyclic carbene) Complexes: Air-Stable 14-Electron Cations and Facile Degenerate C-H Activation
Cationic Ir(III) systems supported by a bis(expanded NHC) framework and featuring both agostic C-H and cis alkyl/hydride ligand sets have been targeted by protonation of the corresponding bis(alkyl) hydride complexes. Remarkably, the steric shielding afforded by the NHC substituents is such that the...
| 主要な著者: | , , , , , , , |
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| フォーマット: | Journal article |
| 言語: | English |
| 出版事項: |
2012
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| 要約: | Cationic Ir(III) systems supported by a bis(expanded NHC) framework and featuring both agostic C-H and cis alkyl/hydride ligand sets have been targeted by protonation of the corresponding bis(alkyl) hydride complexes. Remarkably, the steric shielding afforded by the NHC substituents is such that these and related putative 14-electron cations are air and moisture stable. In solution, degenerate fluxional exchange is brought about by reversible σ-bond activation within the agostic alkyl C(sp3)-H bond; a non-dissociative mechanism is implied by the activation parameters ΔH‡ = 8.8(0.4) kcal mol-1 and ΔS‡ = -12.2(1.7) eu. © 2012 American Chemical Society. |
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