IR spectroscopic characterization of 3d transition metal carbene cations, FeCH2+ and CoCH2+: periodic trends and a challenge for DFT approaches

Frank J Wensink; Corry E Smink; P B Armentrout; Joost M Bakker

doi:10.1039/d4cp00026a

IR spectroscopic characterization of 3d transition metal carbene cations, FeCH₂⁺ and CoCH₂⁺: periodic trends and a challenge for DFT approaches

Phys Chem Chem Phys. 2024 Mar 27;26(13):9948-9962. doi: 10.1039/d4cp00026a.

Authors

Frank J Wensink¹, Corry E Smink¹, P B Armentrout², Joost M Bakker¹

Affiliations

¹ Institute for Molecules and Materials, FELIX Laboratory, Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands. joost.bakker@ru.nl.
² Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112, USA. armentrout@chem.utah.edu.

Abstract

A combination of IR multiple-photon dissociation (IRMPD) action spectroscopy and quantum chemical calculations was employed to investigate the [M,C,2H]⁺ (M = Fe and Co) species. These were formed by reacting laser ablated M⁺ ions with oxirane (ethylene oxide, c-C₂H₄O) in a room temperature ion trap. IRMPD spectra for the Fe and Co species are very similar and exhibit one major band. Comparison with density functional theory (DFT) and coupled cluster with single and double excitations (CCSD) calculations allows assignment of the spectra to MCH₂⁺ carbene structures. For these 3d transition metal systems, experimental IRMPD spectra compare relatively poorly with DFT calculated IR spectra, but CCSD calculated spectra are a much better match primarily because the M-C stretch gains significant intensity. The origins of this behavior are explored in some detail. The present results are also compared to previous results for the 4d and 5d congeners and the periodic trends in these structures are evaluated.