Infrared spectra of methylidynes formed in reactions of Re atoms with methane, methyl halides, methylene halides, and ethane: Methylidyne C-H stretching absorptions, bond lengths, and s character

摘要

Rhenium carbyne complexes (HC ReH3, HC ReH2X, HC ReHX2, [X = F, Cl, and Br] and CH3C ReH3) are produced by reactions of laser-ablated Re atoms with methane, methyl halides, methylene halides, and ethane via oxidative C-H(X) insertion and alpha-hydrogen migration in favor of the carbon-metal triple bond. The stabilities of the carbyne complexes relative to other possible products are predicted by DFT calculations. The diagnostic methylidyne C-H stretching absorptions of HC ReH3 and its mono- and dihalo derivatives are observed on the blue sides of the precursor C-H stretching bands, and the frequency decreases and the bond length increases in the order of H, F, Cl, and Br, following the decreasing s character in hybridization for the C-H bond. The dihalo methylidynes have higher C-H stretching frequencies and s characters than the monohalo species. The rhenium methylidynes have C, structures, and as a result the HC ReH3 and CH3C ReH3 complexes have two equivalent shorter and one longer Re-H bonds, as compared to the tungsten, methylidyne HC WH3 with three equivalent W-H bonds.