Sterically Encumbered Iridium Bis(N-heterocyclic carbene) Complexes: Air-Stable 14-Electron Cations and Facile Degenerate C鈥揌 Activation

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• 作者：Nicholas Phillips ; Johnny Rowles ; Michael J. Kelly ; Ian Riddlestone ; Nicholas H. Rees ; Athanasia Dervisi ; Ian A. Fallis ; Simon Aldridge
• 刊名：Organometallics
• 出版年：2012
• 出版时间：December 10, 2012
• 年：2012
• 卷：31
• 期：23
• 页码：8075-8078
• 全文大小：266K
• 年卷期：v.31,no.23(December 10, 2012)
• ISSN：1520-6041

文摘

Cationic Ir(III) systems supported by a bis(expanded NHC) framework and featuring both agostic C鈥揌 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 蟽-bond activation within the agostic alkyl C(sp³)鈥揌 bond; a non-dissociative mechanism is implied by the activation parameters 螖H = 8.8(0.4) kcal mol^鈥? and 螖S = 鈭?2.2(1.7) eu.