Infrared Spectra of Simple Methylidyne, Methylidene, and Insertion Complexes Generated in Reactions of Laser-Ablated Rhodium Atoms with Halomethanes and Ethane

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Small rhodium carbene complexes, CX2═RhX2, CXH═RhX2, and CH2═RhX2, are identified in the product matrix infrared spectra from reactions of laser-ablated Rh atoms with tetra-, tri-, and dihalomethanes. Evidence for Rh carbynes, XC≡RhX3, is also found in the tetrahalomethane spectra. Calculated Rh−C bond lengths of 1.788−1.820 and 1.730−1.740 A are appropriate for double and triple bonds, respectively. While only the CH3−RhF insertion primary product is observed in the CH3F spectra, weak RhH and RhD diatomic molecule absorptions suggest that the C−H activation product CH2F−RhH, containing a Rh−H bond, also forms during reaction, but subsequently dissociates. The analogous CH3CH2−RhH insertion product is identified in the ethane spectra, in line with the recently discovered CH3−RhH. The observation of RhH and RhD without dihydride or methylidene absorptions in the product spectra suggests that only the insertion complex is generated in the Rh + C2H6 reactions. The present results reconfirm the trend that hig...