Spectroscopic Identification of the Carbyne Hydride Structure of the Dehydrogenation Product of Methane Activation by Osmium Cations

Abstract

The present work explores the structures of species formed by dehydrogenation of methane (CH) and perdeuterated methane (CD) by the 5d transition metal cation osmium (Os). Using infrared multiple photon dissociation (IRMPD) action spectroscopy and density functional theory (DFT), the structures of the [Os,C,2H] and [Os,C,2D] products are explored. This study complements previous work on the related species formed by dehydrogenation of methane by four other 5d transition metal cations (M = Ta, W, Ir, and Pt). Osmium cations are formed in a laser ablation source, react with methane pulsed into a reaction channel downstream, and the resulting products spectroscopically characterized through photofragmentation using the Free-Electron Laser for IntraCavity Experiments (FELICE) in the 300-1800 cm range. Photofragmentation was monitored by the loss of H/D. Comparison of the experimental spectra and DFT calculated spectra leads to identification of the ground state carbyne hydride, HOsCH (A') as the species formed, as previously postulated theoretically. Further, a full description of the systematic spectroscopic shifts observed for deuterium labeling of these complexes, some of the smallest systems to be studied using IRMPD action spectroscopy, is achieved. A full rotational contour analysis explains the observed linewidths as well as the observation of doublet structures in several bands, consistent with previous observations for HIrCH (A'). Graphical Abstract ᅟ.

Sequential activation of methane by Ir+: An IRMPD and theoretical investigation

“…All energy values within this work are reported at 0 K, consistent with previous IRMPD work [13,15,16,27]. To verify that relative 298 K Gibbs energies should not differ significantly from these values, the Gibbs energies for five [Ir,3C,10H] + isomers were explicitly calculated.…”

“…Verification of these assignments has been achieved by examination of the analogous perdeuterated species, [M,C,2D] + , where the importance of including rotational band structure to reproduce the experiment was also demonstrated [15]. Extensions of this work now confirm that the [Os,C,2H] + species formed in methane activation by Os + also has the carbyne hydride structure, but now with no indications of carbene present [16].…”

Carbide Dihydrides: Carbonaceous Species Identified in Ta4+‐Mediated Methane Dehydrogenation

“…HTa 4 CH + ). Carbide dihydrides, as the one uncovered here, represent a class of carbonaceous species, which were typically regarded as energetically unfavorable over other structures [14b, 15a] . However, the present study shows that this assumption may not hold in general and consequently probing for the presence of carbide dihydrides should be included in investigations of reaction intermediates in heterogeneously catalyzed reactions of metals with hydrocarbons.…”

“…[1f, 11] Them ethods have been employed previously to investigate tantalum-based compounds,inparticular bare tantalum cluster cations [12] and cationic cluster oxides. [13] Whereas investigations of atomic cations and their methane dehydrogenation products for different elements [9,14] are rather abundant, including studies of relevant reaction products from other precursor molecules, [15] only af ew studies have addressed the IRMPD spectra of products of methane activation by metal clusters. These studies include the characterization of intermediates from the entrance channel (i.e.m ethane adsorption and insertion of the metal into the CÀHbond) for cationic gold [16] and platinum [17] clusters.…”

Carbid‐Dihydride: kohlenstoffhaltige Spezies identifiziert in der Ta4+‐vermittelten Methandehydrierung

“…Nichtsdestotrotz ermöglicht die theoretische Analyse der gemessenen Spektren, insbesondere die der perdeuterierten Verbindungen, eine eindeutige Identifizierung der Carbid‐Dihydridstruktur (d. h. H 2 Ta 4 C + ), die gegenüber einer Carbin‐Hydridstruktur (d. h. HTa 4 CH + ) dominiert. Carbid‐Dihydride, wie die hier identifizierte Verbindung, stellen eine Klasse von kohlenstoffhaltigen Spezies dar, die typischerweise als energetisch ungünstig gegenüber anderen Strukturen angesehen wurde [14b, 15a] . Die vorliegende Studie zeigt jedoch, dass diese Annahme möglicherweise nicht generell zutrifft, weshalb Untersuchungen das Vorhandensein von Carbid‐Dihydriden als Intermediate in Reaktionen von Metallen mit Kohlenwasserstoffen in der heterogenen Katalyse miteinbeziehen sollten.…”