Issue 2, 2024

Ion mobility mass spectrometry uncovers regioselectivity in the carboxylate-assisted C–H activation of palladium N-heterocyclic carbene complexes

Abstract

Carboxylate-assisted Pd-catalyzed C–H bond activation constitutes a mild and versatile synthetic tool to efficiently and selectively cleave inert C–H bonds. Herein, we demonstrate a simple method to experimentally evaluate both reactivity and selectivity in such systems using mass spectrometry (MS) methods. The N-heterocyclic carbene (NHC) cations [(NHC)PdX]+, bearing as X ligand bases commonly used to promote the C–H activation (carboxylates and bicarbonate), are generated in the gas-phase by ESI-MS. Their C–H bond activation at the N-bound groups of the NHC is then studied using Collision Induced Dissociation (CID) experiments. Ion Mobility Spectrometry (IM)-MS is exploited to identify a number of regioisomers associated with the distinctive site selective C–H activations. It is demonstrated that such C–H activation concomitant with acetic acid release occurs from a mixture of activated [(NHC-H)Pd(CH3CO2H)]+ and non-activated [(NHC)Pd(CH3CO2)]+ complexes. The identity of the X-type ligands (X = Cl, carboxylates and bicarbonate) has a significant impact on the regioisomer branching ratio upon CID conditions. IM-MS in conjunction with a DFT mechanistic study is presented for the acetate-assisted C–H activation of the [(NHC)Pd(CH3CO2)]+ cation featuring butyl and aryl as N-donor groups.

Graphical abstract: Ion mobility mass spectrometry uncovers regioselectivity in the carboxylate-assisted C–H activation of palladium N-heterocyclic carbene complexes

Supplementary files

Article information

Article type
Paper
Submitted
28 Aug 2023
Accepted
26 Nov 2023
First published
27 Nov 2023
This article is Open Access
Creative Commons BY-NC license

Dalton Trans., 2024,53, 656-665

Ion mobility mass spectrometry uncovers regioselectivity in the carboxylate-assisted C–H activation of palladium N-heterocyclic carbene complexes

L. Ibáñez-Ibáñez, A. Mollar-Cuni, E. Apaloo-Messan, A. K. Sharma, J. A. Mata, F. Maseras and C. Vicent, Dalton Trans., 2024, 53, 656 DOI: 10.1039/D3DT02793G

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