Issue 38, 2025

Quantum tunneling dynamics in the Ni+-mediated C–H activation of acetic acid

Abstract

The mechanistic and dynamic properties of the Ni+ mediated reaction with CH3COOH and its perdeuterated isotopologue are presented. Microcanonical kinetic measurements are made in the gas phase with the energy- and time-resolved single photon initiated dissociative rearrangement reaction (SPIDRR) technique and these are complemented with density functional theory (DFT) and multi-reference (MRCI) calculations. Experimental and theoretical evidence indicates that the formation of three product pairs – Ni(C2H2O)+ + H2O, Ni(CH4O)+ + CO and Ni(H2O)+ + C2H2O – are rate limited by C–H bond activation. Measurements of rate-limiting microcanonical k(E) rate constants are made over the 15 000 cm−1 to 20 000 cm−1 (180–240 kJ mol−1) energy range where a transition from quantum mechanical tunneling to over-barrier reaction control is observed. Rate constants, where quantum mechanical tunneling (QMT) primarily contributed to their magnitudes, possessed a large H/D QMT kinetic isotope effect (KIE = 19.0 ± 3.2) consistent with the expectations of QMT. Surprisingly, QMT rate constants in the tunneling energy regime were nearly energy independent and appear to extrapolate to very low energies. Applications of tunneling corrections to RRKM (Rice–Ramsperger–Kassel–Marcus) calculated rate constants failed to describe this unexpected QMT behavior. It is proposed that the Ni+ cation's electronic structure may promote QMT by providing bonding schemes where the proximity of organic fragments increase QMT probability. Such structures are proposed to exist along the multidimensional PES, providing tunneling pathways with reduced barrier widths and consequent energy dependence. These results highlight quantum dynamic properties of Ni+ ions in C–H bond activation reactions, an important step towards understanding the metal's ability to promote catalysis at low energy.

Graphical abstract: Quantum tunneling dynamics in the Ni+-mediated C–H activation of acetic acid

Supplementary files

Article information

Article type
Paper
Submitted
09 Jul 2025
Accepted
31 Aug 2025
First published
11 Sep 2025
This article is Open Access
Creative Commons BY license

Phys. Chem. Chem. Phys., 2025,27, 20838-20853

Quantum tunneling dynamics in the Ni+-mediated C–H activation of acetic acid

G. Pinto, H. Barzinmehr, S. U. Okafor, W. Smith, M. Brdecka, K. L. Benjamin, M. Gutierrez and D. J. Bellert, Phys. Chem. Chem. Phys., 2025, 27, 20838 DOI: 10.1039/D5CP02626A

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements