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

The products of methane dehydrogenation by gas-phase Ta₄ ⁺ clusters are structurally characterized using infrared multiple photon dissociation (IRMPD) spectroscopy in conjunction with quantum chemical calculations. The obtained spectra of [4Ta,C,2H]⁺ reveal a dominance of vibrational bands of a H₂ Ta₄ C⁺ carbide dihydride structure over those indicative for a HTa₄ CH⁺ carbyne hydride one, as is unambiguously verified by studies employing various methane isotopologues. Because methane dehydrogenation by metal cations M⁺ typically leads to the formation of either MCH₂ ⁺ carbene or HMCH⁺ carbyne hydride structures, the observation of a H₂ MC⁺ carbide dihydride structure implies that it is imperative to consider this often-neglected class of carbonaceous intermediates in the reaction of metals with hydrocarbons.