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Ring Slippage and Dissociation of Pentamethylcyclopentadienyl Ligand in an (η5‑Cp*)Ir Complex with a κ3O,C,O Tridentate Calix[4]arene Ligand under Mild Conditions

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posted on 2018-06-12, 14:57 authored by Takuya Kuwabara, Ryogen Tezuka, Mikiya Ishikawa, Takuya Yamazaki, Shintaro Kodama, Youichi Ishii
The first examples of κ3-O,C,O tridentate calix[4]­arene transition-metal complexes [Cp*M­(p-tBucalix­[4]­arene­(2−)-κ3-O,C,O)] (M = Ir, Rh) that are stable both in the solid state and in solution were synthesized. The reaction of the Ir complex with 2 equiv of xylyl isocyanide afforded the (η1-Cp*)­Ir­(CNXy)2 complex in which the Cp* ligand is slipped from an η5 to an η1 fashion, although ring slippage of an η5-Cp* ligand is very uncommon in comparison with that of Cp. The reaction of the (η1-Cp*)Ir complex with additional 1 equiv of isocyanide resulted in the liberation of the Cp* ligand as Cp*H, which was confirmed by 1H NMR. This study provides the first observation of stepwise dissociation of a Cp* ligand from group 4–10 transition-metals via η1 coordination. This unique phenomenon seems to be facilitated by flexible coordination of an OH group in the C-metalated calix­[4]­arene ligand.

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