In-Depth Study on Chloride Abstractions from (NHC)Ir(COD)CI Complexes

Gellert Sipos, Pengchao Gao, Daven Foster, Brian W. Skelton, Alexandre N. Sobolev, Reto Dorta

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Abstract

While attempting to prepare a series of cationic NHC-Ir complexes of general formula [(NHC)Ir(COD)](+) via the silver salt metathesis reaction of its precursor (NHC)Ir(COD)Cl in dichloromethane, we unexpectedly synthesized [(mu-Cl){(2,7-SICyNap)Ir(COD))center dot{Ag(OTf)}], a chlotide-bridged Ir-Ag adduct. This result led us to investigate the chloride abstraction from the (NHC)Ir(COD)Cl systein in detail. We show how the outcome of this ubiquitous reaction is dependent on a fine balance between the nucleophilicity of the weakly coordinating anion (WCA) and the polarity/coordinating ability of the reaction medium. A frequently encountered alternative to using silver salts is also presented and compared. The experimental difference in the reactivitieS of cationic catalysts in a representative intramolecular hydroamination reaction shows how a cationic Ir-Ag adduct can fail to deliver the reaction product through what appears to be a stabilization of the catalytically inactive iridium-silver intermediate by the educt.

Original languageEnglish
Pages (from-to)801-817
Number of pages17
JournalOrganometallics
Volume36
Issue number4
Early online date6 Feb 2017
DOIs
Publication statusPublished - 27 Feb 2017

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